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An electrical outlet box molded of plastic material has a knockout arrangement in a box wall that is formed by inner, intermediate and outer circular grooves that are eccentrically positioned to overlap at a tangent location and define inner, intermediate and outer eccentrically positioned circular

An electrical outlet box molded of plastic material has a knockout arrangement in a box wall that is formed by inner, intermediate and outer circular grooves that are eccentrically positioned to overlap at a tangent location and define inner, intermediate and outer eccentrically positioned circular knockouts. The grooves vary in depth from a minimum depth at the tangent location to a maximum depth opposite from the tangent location. Areas of increased weakness are provided in the box wall at the bottoms of at least the inner and intermediate grooves, and screwdriver slots are provided in the knockouts opposite from the tangent location.

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We claim: 1. A wall having at least one knockout arrangement therein, said knockout arrangement comprising eccentrically positioned inner, outer and intermediate knockouts bounded by inner, outer and intermediate circular grooves in said wall, said grooves overlying one another at a tangent locatio

We claim: 1. A wall having at least one knockout arrangement therein, said knockout arrangement comprising eccentrically positioned inner, outer and intermediate knockouts bounded by inner, outer and intermediate circular grooves in said wall, said grooves overlying one another at a tangent location, said grooves having a common first depth greater than zero at said tangent location and a second depth that is greater than said first depth at a location generally opposite from said tangent location. 2. The wall of claim 1 including at least one area of weakness in said wall within said inner groove spaced from said tangent location, the area of weakness providing little or no strength or resistance against removal of the inner knockout compared to the strength or resistance of the wall around the remainder of the bottom of the inner groove. 3. The wall of claim 2 including at least one area of weakness in said wall within said intermediate groove spaced from said tangent location, the area of weakness within the intermediate groove providing little or no strength or resistance against removal of the intermediate knockout compared to the strength and resistance of the wall around the remainder of the bottom of the intermediate groove. 4. The wall of claim 3 wherein said area of weakness in said wall within said intermediate groove is generally opposite from said tangent location. 5. The wall of claim 1 including a pair of generally opposite areas of weakness in said wail within said inner groove spaced from said tangent location, the areas of weakness providing little or no strength or resistance against removal of the inner knockout compared to the strength and resistance of the wall around the remainder of the bottom of the inner groove. 6. The wall of claim 5 including at least one area of weakness in said wall within said intermediate groove spaced from said tangent location, the area of weakness within the intermediate groove providing little or no strength or resistance against removal of the intermediate knockout compared to the strength and resistance of the wall around the remainder of the bottom of the intermediate groove. 7. The wall of claim 1 wherein each of said inner, outer, and intermediate knockouts has a plane outer surface and an outer periphery, and a slot in said outer surface of each of said knockouts adjacent said outer periphery thereof generally opposite from said tangent location for receiving a flat bladed screwdriver tip. 8. The wall of claim 7 wherein each said slot is a shallow depression having a curved bottom. 9. The wall of claim 1 wherein said second depth is the same for all of said grooves and said grooves extend around a full 360 degrees and reduce the thickness of said wall over a full 360 degrees, and the depth of said grooves being less than the thickness of said wall around at least 75% of the circumference thereof. 10. An electrical outlet box of plastic material, said box having a plurality of walls, at least one of said walls having at least one knockout arrangement therein formed by at least one generally circular groove in said one wall, said groove varying in depth between a minimum depth location and a maximum depth location that is generally opposite from said minimum depth location, said groove depth gradually increasing along inclined arcuate paths around the circumference thereof from said minimum depth location to said maximum depth location, said groove extending over a full 360�� and reducing the thickness of said wall over a full 360��, said groove having a groove bottom and a predetermined groove depth, said groove bottom being interrupted by at least one area of weakness in said wall within said groove that increases the groove depth and further reduces the strength of said wall in the area of said groove compared to the strength of said wall around the remainder of said groove, and the area of weakness occupying not more than 25% of the groove circumference and providing little or no strength and resistance against removal of the knockout compared to the strength and resistance of the wall around the remainder of the bottom of the groove. 11. The box of claim 10 wherein the difference between said minimum and maximum depth locations is 0.005-0.010 inch. 12. An electrical outlet box of plastic material, said box having a plurality of walls, at least one knockout arrangement in at least one of said walls, said knockout arrangement comprising inner, outer and intermediate generally circular grooves in said wall, said grooves being eccentric with respect to one another and overlapping one another at a tangent location, said grooves varying in depth from a minimum depth at said tangent location to a maximum depth generally opposite from said tangent location, the thickness of the wall being reduced by said grooves including along said tangent location, and said groove depth for each of said grooves gradually increasing along inclined arcuate paths around the circumference thereof from said minimum depth location to said maximum depth location. 13. The box of claim 12 wherein said grooves surround inner, outer and intermediate knockouts, each of said knockouts having a plane outer surface and an outer periphery, a slot in said outer surface of each of said knockouts adjacent said outer periphery thereof generally opposite from said tangent location, and said slots having a depth that is not greater than one-half the thickness of said one wall. 14. The box of claim 13 wherein said maximum depth is the same for all of said grooves. 15. The box of claim 12 wherein the difference between said minimum and maximum depths is 0.005-0.010 inch. 16. The box of claim 12 including at least one area of increased weakness in said wail within said inner groove at a location spaced from said tangent location, the area of increased weakness providing little or no strength or resistance against removal of the inner knockout compared to the strength and resistance of the wall around the remainder of the bottom of the inner groove. 17. The box of claim 16 including at least one area of increased weakness in said wall within said intermediate groove at a location spaced from said tangent location, the area of increased weakness within the intermediate groove providing little or no strength or resistance against removal of the intermediate knockout compared to the strength and resistance of the wall around the remainder of the bottom of the intermediate groove. 18. The box of claim 17 wherein said gradually increasing depth of said intermediate groove is interrupted by at least one area of weakness within said intermediate groove located generally opposite from said tangent location and said gradually increasing depth of said inner groove is interrupted by at least two generally opposite areas of weakness spaced from both said tangent location and said location of maximum depth. 19. An electrical outlet box of plastic material, said box having a plurality of walls, at least one of said walls having at least one knockout arrangement therein formed by at least one generally circular groove in said one wall, said groove extending over a full 360 degrees and having a groove bottom, said groove having a predetermined groove depth and said groove bottom being interrupted by at least one area of weakness in said wall within said groove that increases the groove depth and further reduces the strength of said wall in the area of said groove compared to the strength of said wall around the remainder of said groove, the area of weakness occupying not more than 25% of the groove circumference and providing little or no strength and resistance against removal of the knockout compared to the strength and resistance of the wall around the remainder of the bottom of the groove. 20. The box of claim 19 wherein said box wall is severed in said area of weakness. 21. The box of claim 19 wherein there are a plurality of circumferentially-spaced areas of weakness in said wall within said groove. 22. The box of claim 19 wherein said area of weakness occupies not more than 15% of the groove circumference. 23. The box of claim 19 wherein there are at least two knockouts defining inner and outer knockouts formed by small and large diameter generally circular grooves and with said large diameter groove surrounding said small diameter groove, said one box wall having areas of weakness therein within both of said small and large diameter grooves, and said area of weakness in said one box wall occupying a larger percentage of the circumference of said small diameter groove than the percentage of the circumference of said large diameter groove that is occupied by said area of weakness in said wall within said large diameter groove. 24. The box of claim 23 wherein said area of weakness in said one box wall within said small diameter groove comprises a plurality of circumferenfially-spaced areas of weakness. 25. The box of claim 23 wherein said area of weakness in said box wall within said large diameter groove occupies not more than 15% of the circumference of said large diameter groove and said area of weakness in said box wall within said small diameter groove occupies not more than 25% of the circumference of said small diameter groove. 26. A flat plastic wall having inner and outer surfaces, a generally circular groove extending into said wall from said outer surface thereof and circumscribing a knockout having a knockout outer surface, said groove varying in depth from a minimum depth location to a maximum depth location that is generally opposite from said minimum depth location, said groove gradually varying in depth in both circumferential directions from said minimum depth location to said maximum depth location, and a recess in said knockout outer surface closely adjacent said groove at said maximum groove depth location for receiving a tool tip to apply force to said knockout and sever same from said wall. 27. A wall having at least one knockout arrangement therein, said knockout arrangement comprising eccentrically positioned inner, outer and intermediate knockouts bounded by inner, outer and intermediate circular grooves in said wall, said grooves overlying one another at a tangent location, said grooves having a common first depth at said tangent location and a second depth that is different from said first depth at a location generally opposite from said tangent location, the thickness of the wall being reduced by the grooves including along said tangent location, and the depth of all of said grooves gradually increasing along inclined arcuate paths around the circumference thereof from one of said locations to the other of said locations. 28. The wall of claim 27 wherein all of said grooves have generally the same maximum and minimum depth. 29. The wall of claim 28 wherein said minimum depth is at said tangent location and said maximum depth is generally opposite from said tangent location. 30. A wall having at least one knockout arrangement therein; said knockout arrangement comprising eccentrically positioned inner, outer and intermediate knockouts bounded by inner, outer and intermediate circular grooves in said wall; said grooves overlying one another at a tangent location; said grooves having a common first depth at said tangent location and a second depth that is greater than said first depth at a location generally opposite from said tangent location; and the depth of all of said grooves gradually increasing along inclined arcuate paths around the circumference thereof from said tangent location to said generally opposite location. 31. A wall having at least one generally circular groove therein forming a knockout; said groove having a depth that varies from a minimum depth at a minimum depth location to a maximum depth at a maximum depth location that is generally opposite from said minimum depth location; said groove depth gradually increasing along inclined arcuate paths around the circumference thereof from said minimum depth location to said maximum depth location; said knockout having a plane outer surface and an outer periphery; and, a slot in said outer surface adjacent said outer periphery generally opposite from said minimum depth location for receiving a tip of a flat bladed screwdriver. 32. The wall of claim 31 wherein said slot is a shallow depression having a curved bottom. 33. A wall having at least one generally circular groove therein forming a knockout; said groove having a depth that varies from a minimum depth at a minimum depth location to a maximum depth at a maximum depth location that is generally opposite from said minimum depth location; said groove depth gradually increasing along inclined arcuate paths around the circumference thereof from said minimum depth location to said maximum depth location; said gradually increasing groove depth being interrupted by at least one area of weakness in said wall within said groove spaced from said minimum depth location to further reduce the strength of said wall in the area of said groove; the area of weakness being weaker than the wall at the maximum groove depth and providing little or no strength or resistance against removal of the knockout compared to the strength and resistance of the wall around the remainder of the bottom of the groove; and, the area of weakness occupying not more than 25% of the circumference of the groove. 34. The wall of claim 33 wherein said area of weakness is located generally opposite from said minimum depth location. 35. The wall of claim 33 wherein said gradually increasing groove depth is interrupted by at least two generally opposite areas of weakness in said wall within said groove located intermediate said minimum and maximum depth locations, the areas of weakness being weaker than the wall at the maximum groove depth and providing little or no strength or resistance against removal of the knockout compared to the strength and resistance of the wall around the remainder of the bottom of the groove.