A helper-up was a boy or junior laborer employed in traditional underground coal mines to assist the primary haulers. They were stationed at dips or steep inclines in the haulage road to lend extra pushing power when heavy, loaded tubs of coal needed to be moved uphill against gravity.
Heard on the job
We lost momentum on the dip, but the helper-up threw his weight against the back of the tub to get us over the crest.