A block of solid ground intentionally left unmined above a working area during shaft sinking or deepening operations. It acts as a heavy-duty physical barrier, shielding the miners at the bottom from falling debris, dropped tools, or runaway skips. Once the lower section is completed and secured, miners carefully blast and remove the barrier to connect the shaft segments.
Heard on the job
We need to leave a solid pentice here while the crew finishes sinking the next fifty feet.