The Master Lock 4mm stainless steel lockout hasp has a 4 mm diameter shackle to fit smaller lockout points than most lockout hasps, and hinged flanges that close to form eight locking holes for padlocks (sold separately), providing the ability to require multiple authorizations to allow access to one locked out device or energy source. The hasp is made from 316 grade stainless steel for corrosion resistance, and the locking holes accommodate padlock shackles up to 9/16" outside diameter. It measures 5-1/4 x 1-3/4" (13.3 x 4.4 cm) (H x W) with a 1"/2.5 cm inside jaw clearance. (H is height, the vertical distance from lowest to highest point; W is width, the horizontal distance from left to right.) This hasp is part of a lockout/tagout (LOTO) safety procedure required at facilities where devices and energy sources need multiple-person authorization to be accessed safely during maintenance and repair.

Lockout/tagout (LOTO) safety procedures require that lockout devices meet Occupational Safety and Health Administration (OSHA) 1910.147(c)(5) standards for quality assurance. LOTO devices use color, warning labels or tags, and sometimes a physical barrier to help prevent machine operation or power activation during maintenance and repair.

Master Lock manufactures padlocks, combination locks, and related security products. The company, founded in 1921, is headquartered in Milwaukee, WI.