Hi, I guess 'sink' is what your about to do and 'sunk' is after you have done it?
Anyway probably much the same thing. The choice is yours, you can drill your holes to the depth you require with the correct drill bit for your application and then change over to a countersink bit. This is placed over and into each hole and applying pressure to the drill will countersink the hole to whatever depth you wish ( normally only sufficient depth that allows the head of your screw to sit flush or slightly below the surface of what you are drilling into).
Today at Homebase, B&Q and the like, you can purchase the above items seperately or even as a more expensive combined item where you drill and c/sink all in one action, however if you choose this option you are better deciding exactly what size and (maybe depth if applicable) you want to drill before you buy the correct combined version.
kevin mckeever
August 2008