2040 & 2020 drilling guide is an adjustable tool ideal for V-Slot and T-Slot profiles. This guide tool helps with accurate drilling for bolts and bolt caps. This drill guide is designed for 5mm holes on one side for drilling the bolt, and 8.3mm holes on the other side for drilling the bolt cap. It is also handy for helping to cut threads at the end of the extrusion. Remember to insert the extrusion all the way through for the best result.