draw slate

draw slate

[′drȯ ‚slāt]
(mining engineering)
A soft rock, 2 inches to 2 feet (5 centimeters to 0.6 meter) thick, that lies above a coal seam and falls with the coal as it is excavated, or soon after.
References in periodicals archive ?
The creative students from Coleg Menai, near Bangor, have been commissioned by the BBC to draw slate signs for Britain's Strongest Man, to be filmed at Criccieth Castle tomorrow.
PHS' team of 10 students, two teachers and their robot "put on an almost flawless performance to lead all its alliances to win-after-win," the SEI said, as it registered five wins and one draw slate to top all the other 34 teams.