A knife having a blade pivoted to a handle is disclosed with a slidable bolt within the handle, the bolt being extended to lock the blade in an open position and retracted to permit closing of the blade. In one form of the invention, the blade includes a camming portion which retracts the bolt when the blade is opened. Also, a biasing mechanism is provided for urging the bolt into locking engagement with the blade. In another form of the invention, the bolt blade is locked in a closed position until the bolt is retracted. The handle is preferably of a unitary one-piece construction and has walls which define a tapered blade receiving slot. Bushings are held at an angle by these walls so that the bushings bear against the sides of the blade and aid in maintaining the blade in all operating positions. The knife blade is pivoted to the handle in a manner which permits removal of the blade for replacement or repair.