These are polystyrene foam blocks. Some are coloured a light fawn shade ( we painted them so that they looked rather less like polystyrene foam blocks ), and some ( which we acquired later ) are white. They are quite large - up to perhaps 80 × 10 × 20cm - so you can build a respectably large structure rather quickly.
Click either picture for a separate version.
Carrying the bricks - they are light and comfortably sized.
A slightly imposing wall, built in a very short time by very unskilled labour.
We used the bricks in at least two of our services :