Oh and another thing, worth paying particular attention to engraving batteries and chargers if you work on sites a lot.
Often the only place to charge batteries up is in the site cabin (especially on UK sites where the chargers are mains voltage and site power leads are all 110) and there's a lot of people in and out of those cabins.
Sometimes the apprentice gets sent to pick up the batteries for his mentor and won't know for sure what belongs to who and just chucks whatever he can find into the van.
I don't think there are many thieves on sites, but there's a good few people who just aren't sure what belongs to who so accidents happen. Engraving all tools cuts down on almost all of those accidents and even the thieves are far less inclined to steal tools and batteries that are well marked.
Just using permanent marker isn't good enough either because that comes right off with a wipe from a Colorfill worktop solvent impregnated tissue.