Lumber/ladder racks - how do you attach them?

For my shell/camper (which is currently off the truck), I used C clamps to fasten the shell to the bed. For most lumber/ladder racks, what is the common method for attaching them? Drilling holes in the bed rails?

 

I made my own rack, and drilling holes was the way to go. My bed is already rusty with a few holes already, so I didn't care about a few more.

If you use angle iron as a base, it won't take much to hold it in place. If you wan't something that is easier to take on and off, you might try adding an attachment rail to the bedrails, like superstut, e-track, or l-track. I like the flexibility that system provides. Its pretty much what toyota did with their gen 2 trucks.