The Collaborative International Dictionary
Sap roller
Sap \Sap\, n. (Mil.) A narrow ditch or trench made from the foremost parallel toward the glacis or covert way of a besieged place by digging under cover of gabions, etc.
Sap fagot (Mil.), a fascine about three feet long, used in sapping, to close the crevices between the gabions before the parapet is made.
Sap roller (Mil.), a large gabion, six or seven feet long, filled with fascines, which the sapper sometimes rolls along before him for protection from the fire of an enemy.