Molly bolts are fasteners with expandable, threaded sleeves used to secure objects of various weights to a surface. When one is inserted into a pre-drilled hole and the bolt tightened, the sleeves flatten to provide a firm anchor. Molly bolts come in many grip lengths and diameters for varying wall thicknesses and loads. Installing these in drywall is easy, but you should always make sure you are using the right materials and procedures for the most effective result.
Note: Although these anchor bolts are commonly used to affix light and heavy objects on drywall, there are also some for other surface types such as sheet metal.
Step 1 - Prepare Yourself
Since you will be drilling through drywall, put on a good pair of safety glasses first to protect your eyes from dust in the air.
Step 2 - Make a Pilot Hole
Drill a through and through hole into the drywall using either an electric or hand drill with a bit size slightly smaller than the diameter of the molly bolt you have. Although these bolts have pointed ends that you can drive into the wall using a mallet or a hammer, a pilot hole will prevent accidental damage.
Step 3 - Insert the Molly Bolts
Insert the molly bolt, pointed-end first, into the pilot hole and lightly tap the head using a hammer. The amount of force that you need to drive it in depends on the size of your pilot hole. If the diameter of the pilot hole is the same as that of the diameter of the molly bolt, then you only have to apply little force. If the pilot hole is considerably smaller, then you will need to expend more effort. This is why a pilot hole only slightly smaller is recommended. It will provide the best hold with the least trouble.
Step 4 - Tighten to Expand the Anchor
After the bolt is in, use a screwdriver to tighten it until you meet resistance. Make sure not to over-tighten so you don't damage the expandable sleeves; these will be flattening out behind the wall as you turn the driver to provide the anchor.
Step 5 - Loosen Again for Hanging
Loosen the molly bolt a little once the threaded sleeves are fully expanded to accommodate what you are hanging. Reversing about two full turns should be all you need regardless of whether you are hanging picture frames or a heavier objects like a mirror.
You can use molly bolts to fasten even heavier objects such as small shelves. Simply choose heavy-duty bolts with a large diameter for heavy objects rather than the normal size. Also, determine the thickness of your drywall before purchasing your fasteners, as you need the entire length of the molly bolts to pass through the drywall to allow the threaded sleeves to expand properly on the other side.