The top two or three feet of the parapet and the parados (the rear side of the trench) would consist of a thick line of sandbags to absorb any bullets or shell fragments. Sandbags were filled with earth. A filling party usually consisted of one soldier shovelling the earth and two holding and tying the bags. The men stacking the filled bags worked in pairs and were expected to move sixty bags an hour. Research by the British Army suggested that a typical bullet used in the First World War would only penetrate fifteen inches into a sandbag.