In this instructable I will convert a standard Canon EFS 18-55mm. kit lens to EF mount.
Why? Because I can, and because I have a Canon 10D laying around, and not many EF lenses. The 10D has a APS-C sensor, but it is not possible to fit EF-S lenses on it. Any later models will fit the EF-S lenses just fine because of the APS-C sensor, the 10D will work just fine with EF-S lenses, when you have modified the mount.
I'm sure you could mod other lenses aswell.
When you have modded your lens, it will be possible to also use it on full frame DSLR's aswell. If you put an EF-S lens on a full frame camera, there will be heavy vignetting. Just sayin'.
As always, it is not my fault if you break your lens or camera.