Coal mine referred to as "no chicken claw, no sheep tail, no bright joints," what is the meaning of the specific

These are figurative metaphors, in the coal mine is the cable connection joints requirements, referred to as "three no": because all electrical equipment in coal mines require explosion-proof, in order to prevent the generation of electric arcs or sparks, so as not to cause gas explosions or coal dust explosions and other catastrophic accidents.

No chicken claw, no sheep's tail refers to the cable joints must be closed to all the copper wire, is strictly prohibited from being exposed. Exposed a small amount of copper wire called chicken claw, exposed a large number of bundles of copper wire called sheep's tail.

No bright joints is better immediately, is to avoid the cable connection at the copper wire directly exposed in the air.