Abstract: An improved safety utility knife has a hollow handle and a blade which is normally retracted within the handle, but can be extended by squeezing an operating lever. The lever is connected to the blade holder by a toggle linkage having a rearmost pin secured in a discrete support whose position is adjustable. A thumbscrew threaded into the support enables one to adjust the position of the support from outside the handle, and thus change how far the blade protrudes from the handle when the operating lever is fully depressed.

Abstract: An improved safety utility knife has a hollow handle and a blade which is normally retracted within the handle, but can be extended by squeezing an operating lever. The lever is connected to the blade holder by a toggle linkage having a rearmost pin secured in a discrete support whose position is adjustable. A thumbscrew threaded into the support enables one to adjust the position of the support from outside the handle, and thus change how far the blade protrudes from the handle when the operating lever is fully depressed.

Abstract: A utility knife utilizing a standard commercial blade as a handle forming a guide for a blade slide and also serving as a housing for the blade in a retracted safe position. The blade slide is advanced and retracted by a toggle linkage connected with an operating lever pivotally attached to the handle and biased by a spring to a position causing automatic retraction of the blade into the housing when the lever is released. When the lever is grasped and pulled toward the handle for advancing the blade to a use position, the toggle linkage assumes a straight line dead center slide and blade locking position.

Abstract: An alarm system is disclosed for warning personnel at a loading dock that a trailer being loaded has crept away from the dock. In a preferred embodiment, the alarm comprises a box-like housing that can be bolted onto the dock; a clamp that is magnetically held against the outside of the housing and which can be removed for quick attachment to a nearby trailer; and, a spring-loaded cord that is spool fed from inside the housing and connected to the clamp. After the clamp has been attached to the trailer, the alarm automatically arms itself through the use of a novel timing mechanism and spring-loaded actuating arm inside the housing. If the trailer then creeps, it tugs the cord, which causes the arm to trigger the alarm. The alarm stays on but can be automatically shut off by simply replacing the clamp back onto the housing.