The wide area across which the British had to stretch themselves made the supply points and lines of communication very vulnerable. The solution that was derived to protect them was the system of blockhouses.
Initially the blockhouses were to be erected at strategic points such as bridges. However, the idea was expanded to both guard the railway line and the present barriers designed to limit the free movement of the Boers across the countryside. To achieve this, blockhouses were constructed at regular intervals along the railway lines. Troops were stationed in and around each blockhouse and the number of men garrisoned varied. The desire to limit the area used by the Boers led to another expansion of the use of blockhouses. Now they were to be used to protect main roads and ultimately to partition the country into areas that could control the Boer movements.
For the most part, the design of a blockhouse was standard although blockhouses where build using existing structures on some occasions. The designer of the blockhouse, Major Rice RE and the men of the Royal Engineers set up manufacturing units to make the component parts. These were then shipped to wherever they were needed. The standardisation of design meant the blockhouses could be constructed quickly and with parts from different manufacturing units if necessary.
Construction of the blockhouses was the responsibility of the army with guidance and support provided by the Royal Engineers.
The distance between blockhouses was calculated to be able to extent the reach as far as possibly but at the same time to prevent the Boers from passing unnoticed between them. The average distance apart was about 1,000 yards (910 m). Line of sight was vital and this required a greater density of blockhouses in some areas. The gap between blockhouses was filled by wire fences. These fences did not run along the shortest distance between the blockhouses but zig-zagged so that the troops from both blockhouses could fire at the enemy between themselves but without the chance of hitting the other blockhouse.
The first fences were made from barbed wire but experience showed that this could be cut easily. Steel wire ¼ in (6mm) thick was imported to provide a more long-lasting deterrent.
The fences were often connected to cans containing stones or other devices that could alert the troops to movement or activity somewhere along the length of the fence.
The blockhouses impeded the movement of the Boers and contributed to bringing the war to an earlier close than would have been the case if they has not been used.