The Sliding-Blade Pocket Knife: A Spring Catch That Locks the Blade Out or In

A knife whose blade slides out of its handle must hold the blade firmly both out and in, or it can close on the fingers or slide out in the pocket. Eben Moody Boynton of West Newbury, Massachusetts, received US 373,580, dated 22 November 1887, for pocket-knives "in which the blade or blades is or are arranged to slide in and out of the handle", with a flat spring on the blade whose knob projects through a slot in the handle. A retaining recess at each end of the slot takes the spring when the blade is out or in; its back shoulder is square, so a push cannot move the blade, while the front shoulder is inclined, so the catch slides in. Two blades can share one shank, and nut-picks, nail-cleaners, corkscrews or pencils can be sheathed the same way. This rung works out how the catch resists and releases, then makes a hollow handle from tube with a slot and two recesses, and a stainless blade with a spring catch.