This 3-in-1 trammel set can be used in three different ways. First, by using both pins to mark out or scribe an arc. Secondly, by removing one pin and fitting the included HB pencil. Thirdly, by replacing one pin with a paper and card cutter blade which is also included. The trammel bar is 64cm long and is made from a rigid alloy extrusion, creating an accurate marking out tool. The scale is clear plus is marked in both metric and imperial graduations. The trammel heads are made from coated steel and have knurled brass thumb screws. A useful extra is the optional 64cm rail with joining bracket, creating a 128cm trammel set, very useful for taking off measurements or marking out large projects. This is another simple product that works extremely well.