- Roadblocks were constructed to obstruct the free movement of enemy armoured vehicles. Whilst they were permanent structures, often utilising concrete anti-tank cubes, a gap had to be left in the centre to allow the unimpeded passage of friendly traffic, particularly British reinforcements proceeding to deal with any air or sea borne landing.
- In order to be effective roadblocks had to be capable of being closed and opened in a very short space of time, no more than five minutes. The method was normally the insertion of sections of steel rail into previously prepared road sockets.
- The illustration shows one such roadblock although this was an early version and it was found that a more complex 'hairpin' shape of rail was necessary to stop a heavy tank.
- It was important that roads blocks were positioned so where possible use was made of natural anti-tank obstacles, an element of surprise could be introduced and cover such as a house was available for the defending party. At Walberswick, a roadblock was placed close to the company Headquarters, probably just before a fork in the main road leading inland from the village. The initial roadblock may have been of relatively simple design, but in time it probably gained steel rails and was provided with an adjacent pillbox.