Blockhouses, small temporary forts, were initially constructed by the British ROYAL ENGINEERS during the South African War as part of the defences for the railways and were later used as an instrument in the containment strategy.
The first of the blockhouses were constructed by A Troop for the defence of the railway bridges in Natal during the advance for the relief of Ladysmith. Blockhouses were also built along the railway on Roberts' advance on Bloemfontien and then into the Transvaal.
In July 1901, blockhouses, as an instrument in the containment strategy, were erected across open country so that the theatre of war was covered by a network of defensible posts. They were usually sited at a distance of ½ [0.8km] to ¾ [1,2km] of a mile apart. In the intervals between them wire entanglements and other obstacles such as spring guns and other forms of alarms were placed.
By the end of the war about 8 000 blockhouses had been erected, dispersed over a total length of about 3 700 miles [approx. 6 000km].
Later a simpler kind of building was devised to meet demand. It was made of upright wooden posts with a double sheathing of corrugated iron, the cavity between the two sheaths was filled with sand or shingle to render the building bullet proof.
[Royal Engineers Museum, Corps History - Part 9]