Lugs may be removed depending on what they're being installed in.
For instance, they may come with 4 lugs and if your mounting it in an older style door, it may mount up against the door, then you'd remove a certain two lugs. Where a typical over under door, they mount perpendicular and the other 2 lugs would be removed instead.
Some times the lugs screw on or off. Other times you need to bresk off the unneeded ones.
I hope that helps.
Google it, you'll see what I'm talking about.
As a matter of fact, I think bob roberts has an article and he's a hell of a lot better at explaining it