On Fri, 18 Dec 2015 22:58:38 +0000, Malcolm Race wrote:

Permanent Marker. You can buy them in WHS - Staedler or Sharpie with
sharp points. Permanent is a slight misnomer - the ink can be removed
using an alcohol based solvent - Meths or if you don't have any, Gin or
Vodka :-)

+1