The tasks of hanging a heavy cabinet and a light one are not very different. The only complication in hanging a heavy cabinet arises when considering how to hold it in place while you fasten it to the wall. You can save your back, and that of the friend you were planning to ask to help you, by temporarily attaching a simple support on the wall and resting the cabinet on that. When the cabinet is hung, you can simply remove the support and patch a few holes.
Things You'll Need
Phillips screw bit
1/4-inch drill bit
Lag screws, 3 inches by 3/8 inch
Make a mark on the wall where the bottom of the cabinet will be. Take the doors off of the cabinet.
Use a stud finder to locate the wall studs. Alternatively, you can knock on the wall until you hear the solid sound of wood.
Set the two-by-four on the mark and, using the level to make sure it is horizontal, screw it into the wall studs with 3-inch screws. If these are sunk 1 to 1-1/4 inches into the studs, they will be literally strong enough to stand on and will easily support pretty much any cabinet. Ensuring that the two-by-four is level will save you the step of leveling the cabinet while you are holding it in place.
Lift the cabinet into place and set it on the two-by-four. Have a friend hold it while you drill 1/4-inch pilot holes through the structural frame inside the cabinet into the wall studs. Drill holes for as many lag screws as will hold the cabinet securely.
Use a socket wrench to screw lag screws into the holes, being sure that they sink well into the studs. They should sink about 1-1/4 inches, but no deeper, as you don't want to screw into any electrical wires that may be there.
Remove the two-by-four. Patch the screw holes with a little spackle or drywall joint compound. Touch up with paint, if desired.
While the use of lag screws will ensure the stability of any cabinet, it may seem like overkill for cabinets weighing less than 50 lbs. If this is the case, use 3-inch screws instead.
In the event that you cannot attach the cabinet to wall studs, do not attempt to attach a heavy cabinet to drywall, or use drywall anchors. Although some drywall anchors are rated for 60 pounds or more, they are not recommended. A good forward jolt may pull them right through the drywall. This is especially true if you live in an earthquake zone.
Don't use screws that are too long. They may hit electrical wires in the stud.