Summary

this tiny thing turns your Steel Right Measuring Angle Square Ruler into marking gauge.

for assembling you need also:
1x Steel Right Measuring Angle Square Ruler (27x0.8mm)
1x M4 x 20 Cross recessed raised cheese head screw (DIN-EN-ISO 7045)
2x M4 Hexagon nut (DIN-EN-ISO 4033)