●You may cut glass plates of up to 20 cm wide, and of any length. ●The white measuring plate can be removed, if your TLC plate happens to be too thick to fit (usually when cutting preparative TLC plates). ●The side screw fixed onto a turning-knob is for controlling the stop position of the scribbler, so that one can prevent the scribbler from cutting off of the glass plate and chipping off a small piece. ●Usually, start from the far side relative to the screw, and cut towards the screw. ●The cutter head can be replaced once it has become worn, which an extra spare is included in your purchase. More are available from us.