Show here is one of the DISTOs in its fixture, that allows the precise adjustment to point the laser beam onto the target on the other side of the nave. The black box in the front is the power supply for the DISTO. Clearly visible is the hole through the wall. The space where the DISTOs are mounted is so narrow that only one person fits between the DISTO and the opposite wall (is about 60cm to the left). In operation the DISTOs are protected by an aluminium hood (that's outlines are marked on the wall).