Sap-roll′er.
(Fortification.) A large roller kept in advance of the men engaged in sapping. It is rolled along at the head of the sap for the protection of the excavators. The sap-roller is a gabion, 6 feet long and 4 feet in diameter, rendered bulletproof by an internal gabion of the same length and 2 1/2 feet in diameter, the space between being filled up with stout wooden pickets. It is sometimes stuffed with wool. It is pushed forward by a sap-fork.