Hmm.. I thought Dar701's suggestion was the only way to do it.. Make sure you drill the holes slightly undersized and finish them with a round needle file. If there's any slop, the movement/recoil will eventually ovalize them. You're probably gonna need a cobalt drill bit, too. You can get those at Cdn. Tire or Home Depot. If I recall, the rails come already tapped, with button-head screws... Is there a vendor selling plain rails without hardware?
There is a method of installation involving rivets, but it's for a specific rail, and it's done in the factory with extra long rivets that go right through the receiver to the other side, replacing the standard receiver-width rivets holding the parts in place. What rifle are you installing this on in particular?
Hope this helps