The boxes are made of 12mm marine ply and there are nest concaves in all compartments. There is a gap between the box and the wall for bats.
Darren has already got Swifts interested in these boxes, so, if he keeps going with his CD, he has every chance of new occupants this year.
It is important that Swift boxes do not spoil the appearance of a nice house, and painting the boxes to match goes a long way to achieve this.
In cases like this, it can be a good idea to mix coarse sand with the paint (1 part sand to 3 parts paint), especially on a rough cast house, and also as there is some evidence that Swifts prefer a rough exterior.