Do you have a question about the SW-Stahl 26118L and is the answer not in the manual?
Initial step involves removing the spark plug from the engine.
Screw gauge adapters into the spark plug threads for measurement.
Attach gauge and set depth to show TDC value without piston impact.
Rotate crankshaft to find the highest reading on the gauge.
Rotate the gauge ring to set it to the 0-position.
Determine piston position relative to TDC by rotating the crankshaft.