Zillebeke - redoubt posts constructed in late 1917

[bierlijn]

Does anyone know the history of a series of 'Posts' constructed to the east of Zillebeke around the end of 1917?

Below are two maps and an aerial.

Map 1 - Map shows British Front Line 24th October 1917, and to the west of that, finger nail shapes hand drawn onto the map.

Map 2 - March 1918 map names these as posts and shows them as short trench echelons with a strongpoint behind.

Photo: One of these seen from the air.