After you’ve drilled the lag bolts into the stud, drill holes where they’ll hit the back of the shelf with a 3/8-inch drill bit.  Photo 4 of 6 in How to Build a Floating Shelf

How to Build a Floating Shelf

4 of 6

After you’ve drilled the lag bolts into the stud, drill holes where they’ll hit the back of the shelf with a 3/8-inch drill bit.