This simple accessory prevents your tape measure from slipping off the corner while measuring diagonals. The 90° inside corner securely straddles any outside corner, and rotates 360° to accomodate any rectangular object. It attaches easily to your tape with a single, powerful rare earth magnet. Use it while assembling drawers for a perfectly square batch. Also great for cases, frames and more. Slot for tape hook measures 1-1/8" wide. Made of durable plastic.