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A folding ladder includes a hinge assembly having first and second ladder hinge plates each defining a plate opening and a plurality of locking slots. A housing is associated with the first ladder hinge plate and extends through the plate openings to provide a rotation axis for the plates, and the s

A folding ladder includes a hinge assembly having first and second ladder hinge plates each defining a plate opening and a plurality of locking slots. A housing is associated with the first ladder hinge plate and extends through the plate openings to provide a rotation axis for the plates, and the second plate is operable to rotate relative to the first plate about the rotation axis to selectively align slots of the first and second plates. A key outside the housing selectively engages aligned slots to selectively prevent rotation of the ladder hinge plates about the rotation axis and is operated by a manual rotation member. An extension ladder includes a pair of nested outer and inner ladder rails. Ladder rungs connected between and the inner rails define a plurality of supporting openings and the inner rails include outer bearing surfaces associated with the supporting openings. An extension latch mechanism having a pivoting dog is coupled to an outer rail and engages the supporting openings and outer bearing surfaces to support the ladder in an extended posision.

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What is claimed is: 1. A ladder hinge assembly comprising: a first ladder hinge plate defining a first plate opening and at least one first locking slot in communication therewith; a second ladder hinge plate defining a second plate opening and at least one second locking slot in communication ther

What is claimed is: 1. A ladder hinge assembly comprising: a first ladder hinge plate defining a first plate opening and at least one first locking slot in communication therewith; a second ladder hinge plate defining a second plate opening and at least one second locking slot in communication therewith; a housing extending through the first and second plate openings, wherein the housing is associated with the first plate and the interior of the second plate opening bears against the exterior of the housing to provide a rotation axis for the plates, and wherein the second plate is operable to rotate relative to the first plate about the rotation axis to selectively align first and second locking slots; a key outside the housing operable to engage aligned slots to prevent relative rotation of the plates about the rotation axis when the key is engaged with the aligned slots; a manual rotation member operably coupled to the key to selectively disengage the key from at least one of the aligned slots by rotation of the member a predetermined amount from a rotation member resting position; and a biased piston inside the housing and operably associated with the key to bias the key into engagement with aligned slots of the plates; wherein the manual rotation member is operably associated with the piston to rotate the piston relative to the housing, the piston including a first bearing surface for operable contact with a second bearing surface of the housing when the manual rotation member is rotated, wherein at least one of the first and second bearing surfaces is a ramped surface and rotation of the manual rotation member is operable to cause rotational and translational relative movement of the piston and the housing. 2. The ladder hinge assembly of claim 1 wherein the predetermined amount is less than 180 degrees. 3. The ladder hinge assembly of claim 1 wherein the ramped surface is ramped at an angle of greater than 15 degrees. 4. The ladder hinge assembly of claim 1 wherein the housing is integrally formed. 5. The ladder hinge assembly of claim 1 further comprising at least one biased plunger operably associated with the piston and the housing to yielding hold the piston and the housing in a relative orientation to maintain the key out of engagement with at least one slot. 6. The ladder hinge assembly of claim 5 wherein the plunger is on the piston and is biased to engage an opening in the housing. 7. The ladder hinge assembly of claim 6 further comprising a cam operably associated with the second ladder hinge plate and including a cam surface operable to dislodge the plunger from the opening in the housing when the hinge plates are rotated a predetermined amount. 8. The ladder hinge assembly of claim 1 in combination with ladder rails wherein the ladder hinge plates are operably associated with a pair of the ladder rails to form a hinged ladder. 9. The ladder hinge assembly of claim 1 in combination with ladder rails wherein the hinge plates are attached to the ladder rails to form a hinged ladder. 10. A ladder hinge assembly comprising: a first ladder hinge plate defining a first plate opening and at least one first locking slot that extends entirely through the first ladder hinge plate; a second ladder hinge plate defining a second plate opening and at least one second locking slot; a housing associated with the first plate and extending through the first and second plate openings, wherein the second plate is operable to rotate relative to the first plate about a rotation axis defined by the housing to selectively align first and second locking slots; a key translatable in a direction substantially parallel to the rotation axis of the plates to selectively engage the slots when aligned to prevent relative rotation of the plates about the rotation axis when the key is engaged with the aligned slots; and a manual rotation member operably coupled to the key to selectively disengage the key from at least one of the aligned slots by rotation of the rotation member a predetermined amount from a rotation member resting position; and a biased piston inside the housing and operably associated with the key to bias the key into engagement with aligned slots of the plates; wherein the manual rotation member is operably associated with the piston to rotate the piston relative to the housing, the piston including, a first bearing surface for operable contact with a second bearing surface of the housing when the manual rotation member is rotated, wherein at least one of the first and second bearing surfaces is a ramped surface and rotation of the manual rotation member is operable to cause rotational and translational relative movement of the piston and the housing. 11. The hinge assembly of claim 10 wherein, when engaged with the aligned slots, the key extends entirely through the first locking slot. 12. The hinge assembly of claim 11 wherein the housing defines an outer cylindrical surface that provides the axis of rotation for the hinge plates. 13. The hinge assembly of claim 10 further comprising a biased plunger inside the housing and operable to yieldingly retain the key disengaged from at least one of the aligned slots. 14. A ladder hinge assembly comprising: a first ladder hinge plate defining a first plate opening and at least one first locking slot that extends entirely through the first ladder hinge plate; a second ladder hinge plate defining a second plate opening and at least one second locking slot; a housing associated with the first plate and extending through the first and second plate openings, wherein the second plate is operable to rotate relative to the first plate about a rotation axis defined by the housing to selectively align first and second locking slots; a key translatable in a direction substantially parallel to the rotation axis of the plates to selectively engage the slots when aligned to prevent relative rotation of the plates about the rotation axis when the key is engaged with the aligned slots; a manual rotation member operably coupled to the key to selectively disengage the key from at least one of the aligned slots by rotation of the rotation member a predetermined amount from a rotation member resting position; and a biased plunger inside the housing and operable to yieldingly retain the key disengaged from at least one of the aligned slots.