The Cardsharp utility knife, by UK-based Iain Sinclair Design, is an ingeniously-designed stainless steel knife that unfolds into a credit-card-sized shape for storage and transport. When closed, the rectangular shape protects the blade and the carrier from accidentally cutting themself; when open, the folding surfaces are arranged so that a corner of the rectangle serves as a miniature hilt, keeping the user's finger from sliding onto the blade.
Originally intended for emergency surgical and first aid applications, the Cardsharp has since been embraced by campers and outdoor enthusiasts looking for an easy-to-carry, compact cooking knife. Made from stainless steel and polpropylene, it weighs just 13 grams, about half the weight of a conventional folding knife. The hinge mechanism itself has been carefully designed for durability and, unlike a conventional "living hinge," is projected to last for an infinite amount of openings and closings, backed up by a lifetime guarantee. Check out how it opens and closes (and yes, it locks into position):