An apparatus for defining a passageway through a composition between first and second locations. The apparatus has a cable pulling assembly and a support for the cable pulling assembly. The cable pulling assembly has a capstan assembly, with a part of the capstan assembly guided in movement around a first axis and engageable with a cable connected to a mole so as to cause a cable engaged by the part of the capstan assembly to be pulled as the part of the capstan assembly is driven around the first axis. The part of the capstan assembly has a circumferential groove, bounded by a surface and extending around the first axis, for reception of a cable to be pulled. The groove is configured so that a circumferentially localized force is applied by the groove surface to a cable operatively positioned in the groove tending to avoid circumferential slippage between the part of the capstan assembly and the cable operatively positioned in the groove.