Master Lock® Safety Lockout and Padlocks Safety lockouts allow up to size workers to lockout a single energy source. Plated to resist rust. Accepts padlocks up to 3/8" shackle diameter. Available in two sizes, 1" and 1-1/2". High security Master Lock® padlocks are 1-1/2" wide with 9/32" shackle. Available in black, blue, green, red, white and yellow bumper colors to provide easy visual identification.