For about $25 you can buy an adjustable guide for perfectly hanging pictures or shelves with two keyhole mounts on their reverse side. It is nice, easily adjustable, and machined from aluminum. But, I wanted to hang only a few shelves.
I tried mounting one or two by measuring and marking. I do not know what happened, but one side of the shelf is higher than the other.
This Instructable will show how to use scrap corrugated cardboard or thin plywood and finish nails to mark the holes very accurately.
- Corrugated cardboard
- Two finish nails
- Screw anchors for drywall
- Marking gauge (or combination square)
Step 1: Cardboard Template
Find a piece of corrugated cardboard with at least one straight edge and as large as the shelf you are hanging. If you cannot find a piece of cardboard that large, it should be at least large enough to cover both keyhole screw mounts.
Step 2: Marking the Cardboard
Align the straight edge of the cardboard with the keyhole screw mounts. Carefully make a pencil mark to indicate the center of the opening on each keyhole.
Step 3: Set Marking Guide
I am using a combination square as a marking gauge to indicate the distance from the top of the shelf to the center of the screw's position in each keyhole mount.
Step 4: Mark the Cardboard Again
I used the combination square to mark from the straight edge of the cardboard in the area where the mark is located showing how far apart the centers of the keyholes are. See the text box in the photo.
See the second photo. Use the square from the straightedge of the cardboard to extend the mark that locates the center of the keyhole. The intersections of the two lines shows the locations of the two mounting screws.
Step 5: Finish Nails
If you are using corrugated cardboard, twist a finish nail to push the point slightly through the cardboard. If you are using 1/4 inch plywood or Masonite, drill holes slightly smaller than the diameter of the finish nail. Tap the nails into the holes.
Step 6: Mark the Wall
Place the cardboard against the wall with its straightedge on top. Place a level on the straightedge. Adjust until the cardboard is exactly where you want the shelf to be. (If your cardboard is smaller than the shelf, make a center mark between the nails. Use it to locate where the center of the shelf should be.) While holding the level and cardboard with one hand, tap the nails with a hammer to mark the centers of the screw mounting holes.
Step 7: Mount the Anchors and the Shelf
To be very precise, drill a small pilot hole into the indentations left by tapping the nails. Drill the holes larger to fit a drywall anchor. (While drilling the pilot holes you can tell if one of the holes will be over a wall stud. If that is the case, drill that hole only large enough for the screw to hold in the wood of the stud.)
With trial and error turn each screw into the wall until it is tight enough to hold the shelf firmly against the wall, but still loose enough for the keyhole mounts to slide onto the screwheads.