On the terrain surface, or from a excavation pit excavation, a trench is first lifted in the same direction as the planned trench wall. In this, the guide walls are created, which represent a kind of template for the diaphragm wall. The guide walls ensure, inter alia, The uppermost slit zones where there is insufficient hydrostatic pressure of the contactor suspension and the suspension level fluctuates in the soil excavation. The guide walls also have the task of guiding the slot wall gripper as well as holding the reinforcing basket and the cut-off pipes laterally. The reinforcing cage is suspended from the guide wall for the exact observation of the correct height. The guide walls further facilitate the detachment of the individual slot wall elements for the orientation of the device guide.

The guide walls are between 0.15 m and 0.25 m thick and generally reach a depth of 0.70 m to about 1.70 m, while for special constructions larger guide wall heights are possible. The depth depends on the fluctuations of the mirror of the supporting fluid during the excavation, the possible loading by lateral loads as well as the depth of any existing power or obstacles. In addition to the control walls, which are mostly made in in-situ concrete, concrete parts are also used. The concrete slabs are concreted in concrete to form a continuous guide wall in preparation for the slab walls. The dimensioning of the control panels is based on the earth pressure, which is determined when the external stability is demonstrated.