Metal Detectable Safety Knife - Smartcut Lightweight, Disposable and Cost Effective The SmartCut safety knife is a lightweight disposable safety knife. Designed for use by both left- and right-handed workers. Featuring a sealed handle with a 14mm blade extension and a non-replaceable stainless steel blade, and incorporates an automatic blade retraction on release of the slider. The spring loaded blade retract system is designed to respond to any uncontrolled move if and when the thumb (push slider) is NOT in forward position. This is a surefire safeguard against serious injury. This knife can be safely pocketed without fear of accident.