back holes

back holes

[′bak ‚hōlz]
(mining engineering)
The holes which are shot last in mine shaft sinking.
References in periodicals archive ?
RNRC0016 and 29 are forward and back holes to RNRC0017 and RNRC0003 respectively.
Both the male pins and female receptacles are terminated with back holes for the attachment of fine gauge instrument wires.