FrameHanger

Reference line is the line you hang everything on — an eye height. The presets are the three accepted conventions: 1450 mm is the 57-inch museum standard, 1500 mm is the metric gallery line, and 1575 mm (62 inches) suits taller rooms and is this app's default. Keep it the same across a room and the wall reads as one piece.

Taut wire: lay the frame face down, hook a finger under the wire and pull it up towards the top of the frame as hard as the picture will pull it on the wall. Measure to that point, not to the slack wire.

Two hooks: resting on two spread hooks the wire cannot rise as high as it does pulled to a single point, so the nails go lower than the one-hook answer — the app works the drop out from the wire's length. Measure the anchor span between the two points the wire is tied to (D-ring to D-ring, centre to centre), and the height of those anchors from the same edge as the taut wire. Hook spacing is yours to choose — mark the wall where the frame's centre goes, then half the spacing each side. Keep the two hooks level.

Hook offset is how far the nail hole sits above the little cradle the wire rests in. Most single brass hooks are 8–12 mm. Drive a nail into a scrap, hang the hook, and measure it once. A screw or a hook whose nail passes through the cradle is 0.

Tape case height: stand the tape on the floor on its base. The blade reads zero at the top of the case, so the lock-out figure is the nail height less that. Lock the blade, stand the case on the floor, and the tip of the blade is your mark.