Scalpel Handle #3 Flat Design (Fits Blades #10, #11, #12, #15, #16). Scalpel Handle #4 Flat Design (Fits Blades #20, #21, #22, #23, #24, #25, #26). Scalpel handle #3 and #4 with scale are reusable instruments used in surgical procedures to provide a secure grip for attaching scalpel blades. The size refers to the handle's thickness and accommodates a wider variety of hand sizes than smaller sized handles. The scale, is a ruler engraved onto the side of the handle, allows for precise measurement during cutting.