The range of the weapon could be altered through a valve mounted on top of the weapon. Excess propellant gasses escaped though a pipe mounted on top of the barrel.
At some ouvrages with AT moats (e.g. Hackenberg, Hochwald) the model 1935 mortars were installed in combat blocks, most of the time on the lower level of a block, shielded by the contrescarp (steep outer slope) of a moat.
A disadvantage of the weapon was that when mounted in a cupola, the barrel was vulnerable since it stuck out quite some cm’s.
Around 1600 mortars were delivered in 1940, but not all of them were installed. For example, only around 1009 were installed in GFM cloches. The ones that were installed, fulfilled an important role of clearing the craters around fortifications, created by German artillery, which were used by attacking soldiers as cover.
This mortar was removed in large numbers from the Maginot fortifications, and re-used in the Westwall, were they were fitted on German designed mountings.
As you can see in the large image on the left, the embrasure of a basement firing chamber is hidden from view by building it into a dry moat. This way, enemy fire (e.g. anti-aircraft artillery (often used against infantry targets) or anti-tank guns) can’t hit it.