Prevent Unintentional Energization of Electric Circuits. Versatile covers lock out most circuit breakers. No. 491 oversized breaker device fits toggle switches to 2-1/2" wide x 7/8" thick. No. 492 for single pole circuit switches having recessed side-holes. No. 493 with convenient thumbwheel, for 277 and 120 volt switches. No. 494 with convenient thumbwheel, for 480/600 volt switches. No. 495 universal multi-pole devices for breakers with tie-bar. Position cover over switch (in "OFF" position. Secure. Apply padlock. Use Master Lock No. 7C5RED padlock for maximum locking flexibility. No. 490 fuse blockout, with a tag, provides effective OSHA tagout of a fuse block.