SQUARE CHECK, from Rockler Woodworking and Hardware, is a simple accessory that prevents your tape measure from slipping off the corner of a material while measuring diagonals.
The 90-degree inside corner securely straddles any outside corner and rotates 360 degrees to accommodate any rectangular object. It attaches easily to your tape with a powerful earth magnet and the slot for the tape hook measures 1-1/8" wide. It can be used while assembling drawers, cases, frames and much more, according to the company. Made of durable plastic, the Rockler Square Check is priced at $4.49. Contact: Rockler Woodworking and Hardware. Tel: 800-233-9359. www.rocklerpro.com