Stops tape measure from slipping off corners while measuring diagonals. The 90° measurement angle securely straddles any corner and rotates 360° to accommodate any rectangular object. Attaches easily to tape with powerful rare-earth magnet. Made of durable plastic. For use while assembling drawers to create perfectly square batch. Also great for cases, frames and more. Slot for tape hook width 29mm (1-1/8"). 1-1/8"