The most basic piece of picture-hanging hardware is the screw, the size of which is based on shaft dimensions (gauge) and threading. To simplify the identification of smaller, more commonly used screw gauges, a numeral designation preceded by a crosshatch symbol has been adopted, with #0 being the smallest and #15 the largest. The most commonly used screw gauges in framing are #4, #6, and #8.
Wood screws (A-1) have a coarser pitch (fewer threads per inch) than sheet metal screws, and often the shafts of wood screws are unthreaded just below the head. Because there are no threads to catch the wood along the smooth portion of the shaft, a wood screw can pull one piece of wood flush against another. Metal screws (A-2, above) have sharp threads that cut into materials such as sheet metal, plastic, or wood. They make excellent fasteners for attaching metal hardware to wood and are preferred for this use because of their fully threaded shafts
D-rings, whether of the single-hole, two-hole, or strap-hanger variety, are an excellent choice of picture hanger (see C-1, C-2, and C-3).
When installed with #4, #6, or #8 pan- or round-head screws, D-rings lie flatter against the wall than screw eyes (a popular but poor choice of hanger—more about those below). You may position single-hole D-rings to match the 60-degree angle recommended for hanging wire; D-ring strap hangers usually end up at an angle more vertically oriented.
Heavy-duty D-rings and strap hangers, constructed of doubled steel, are intended for hanging heavy wood frames, large gallery wraps, or cradled boxes, and you can use them with or without picture wire. When using them without wire, align the D-rings or strap hangers vertically at the upper corners on the back of the frame. Then suspend the picture directly on substantial picture hooks or screws anchored into the wall.
Another excellent choice of picture hanger is the Super Steel Hanger (see E-1 and E-2). These are steel plates with either two or four screw holes located both above and below a ring, to which you attach the picture wire.
A four-holed, steel-plate hanger easily supports a frame of up to 100 pounds, while the shorter two-hole style holds up to 50 pounds. Mount the center of this hardware one-quarter of the way down from the top edge of the frame, either centered on a narrow moulding or about ½ inch from the inner edge of a wider moulding. Use #4 or #6 screws.
Sadly, the two most popular types of picture-hanging hardware aren’t the strongest or most effective. Consider the following cautionary framing tip before grabbing a sawtooth hanger (D-1) or a screw eye (D-2). A sawtooth hanger is a jagged-edged, metal strip, 1 to 2 inches long (D-1). It’s popular because of its simplicity and the ease with which it can be installed, but it has a high failure rate. This is not the result of weakness of the metal strip, but rather of the softness of the frame moulding and selected fastener.
Most sawtooth hardware comes with short 3⁄8– to ½-inch tacks that press into the wood of a painted panel or frame. If the wood is soft—like pine—nails can pull out of the frame due to the weight of the framed work and the pull of gravity. Substituting small #3 screws for the tacks greatly improves the holding strength. Snap-in sawtooth hangers, used with metal frames, require no screws and won’t pull out. Even at their best, however, sawtooth hangers should never be used for hanging fine art because a picture can easily be knocked from the sawtooth. Galleries generally don’t accept framed art with sawtooth hangers of any kind.