Ladders and hinge for ladders

Ladders and ladder components are described herein, including multipurpose and adjustable ladders. In one embodiment, a ladder includes a first assembly having rails and rungs, a second assembly having rails and rungs, and one or more hinges coupling the first and second assemblies together such that the first and second assembly may be positioned relative to one another in at least a position or state and at least a second position or state. The ladder is adjustable by moving a pin from a locked state in which it is located in a recess or slot of the hinges and prevents rotation of the hinges to an unlocked state in which it is removed from the recess or slot. Multiple joints can be simultaneously transitioned between locked and unlocked states using a releaser to move the pin, and a spring can bias the pin into a locked state.