A type 28a concrete pillbox emplacement for a 6 pounder Hotchkiss anti-tank gun. There remain a number of this type of emplacement around Sibsey, Stickney and Stickford. They are all equipped with the holdfast with 9 bolts which was designed to accommodate the 6 pounder Hotchkiss gun. Originally intended for naval use, this gun was put into First Word War tanks many of which were built in Lincoln and then in store. Many of these emplacements were constructed in the GHQ line where they were given different embrasures and the fittings for the scarce 2 pounder anti-tank gun. {1}{2}