45 degree turn: how much to cut

The everyday angle on site. The cut is a quarter of a 90 degree one, it marks out simply and folds without a fight. On 300 mm tray it is 124 mm each way from the bend line, on 200 mm it is 83 mm, on 100 mm it is 41 mm.

Why 45 suits most jobs

The wedge stays small, the metal does not buckle at the fold, and two of them in a row give a right angle — which is why 45 degrees covers most of what a run needs. There is another convenience: the full opening comes to roughly eight tenths of the tray width, so you can size it in your head without reaching for a phone.

Marking out

Mark everything on straight tray before bending: once the first fold is made the geometry shifts and the figures go out. Start with the bend line across the base, then measure off it both ways along the inner edge. The wedge tip goes on the outer edge, on the bend line. You cut the base and one side — the one that ends up inside the turn.

Two turns in a row

To clear an obstruction and come back on the original line, two 45 degree turns are set facing each other, with the notches on opposite sides. Getting the distance between them right matters: it has to allow for the metal taken out by the cut, or the pieces will not line up.