This is a part, to transform your 30x1mm steel ruler of any length into a marking gauge.
You will also need a M4 nut and M4x30mm screw.
I heated the screwhead with a creme brulee torch and prest it into the grip piece.
You can also mold the hot and soft plastic around the head, if you want to, while pressing the hot screw in the pocket.
Press the nut into the hole and you are done.
Simply shove it over the ruler to the desired depth and secure it with the screw.