Key facts
- Official designation: FW3/24
- Shape: Irregular hexagonal
- Five faces of 8ft (2.4m) in length externally and a rear face of 13ft (3.96m) with two rifle loops and an entrance 2ft (61cm) wide.
- Those with thinner walls (up to 15ins) have rifle embrasures built in; the thicker-walled version (up to 24ins) has pre-formed embrasures designed to accommodate light machine guns (LMG’s).
Information obtained from pillbox typology part 2 in Loopholes journal of the PSG. With kind permission of Mike Osborne.

Large Shellproof Type 24 Pillbox with chamfered roofline along GHQ Line A.
FW3/24 Shellproof
This type can be found along the route of GHQ Line A in Hampshire and Line B in Surrey with all walls built to a thickness of 51″, examples found beside the River Mole have provision on lower walls to hold trail legs for the Bren Gun tripod. Between Chilworth and Dorking in Surrey via the route of the North Downs Way dozens of Hexagonal shellproof Type 24 Pillboxes can be found dug in to the high chalky slopes and woodland. Variations in loopholes depth and wider mountings points were provided for the operation of the Boys Anti Tank Rifle on its T shaped bipod.
All examples have either elongated X or Y shaped inner blast walls, regional loophole variations include cast concrete embrasures or just a plain brick opening. Angled off or chamfered roof edges as as aid to deflect enemy fire, this is more commonly seen on dug in defences.
- Shellproof FW3/24 @ TQ229487 Betchworth Surrey
- Inside showing Bren Gun tripod leg location slots
- Back of pillbox showing its two cast embrasures

Interior of shellproof Type 24 Pillbox, Basingstoke Canal. Looking to rear with side loophole, rear loophole and interior blastwall, note corrugated iron ceiling shuttering and wooden table batten edge of shelf top.

A Shellproof Type 24 Pillbox with entrance protected by an L shaped blastwall, Slaugham, West Sussex.