Tracer Tools ADP2 Deep Hole Construction Pencil. 

The perfect tool for Carpenters, Joiners, Kitchen Fitters and DIY enthusiasts alike.
Thanks to its unique 120mm retractable, interchangeable leads, the TRACER deep hole pencil can mark through beams & joists with ease. 

Shirt / Trouser Clip
Mark 100mm depth in a 3mm diameter hole 
Mark 145mm depth in a 6mm diameter hole
Long and sturdy metal shaft

If you make it Tracer will mark it : If you fix it Tracer will mark it