Rotate Layer

Right-click the Layers table on the Chute Faces tabsheet and choose Rotate Layer... to rotate every face in the currently selected layer about an axis and a rotation point, without having to move each vertex by hand.

the Rotate Layer dialog
The Rotate Layer dialog

Choosing the rotation

Click Rotate to apply. The vertices are left with full decimal precision (not rounded), so rotating a layer and then rotating it back by the same angle returns it to its original coordinates exactly.

Belt velocity rotates with the layer

If the layer has a non-zero belt velocity (Vx, Vy, or Vz in the Layers table), those velocity components are rotated by the same angle as the geometry – so you can set a belt's velocity along one axis (e.g. Vx = 5 m/s) and then rotate the whole layer into its final orientation, rather than having to recompute the velocity vector by hand afterward. A layer with zero velocity is left untouched (there's no direction to rotate).

Face Desc values entered by Draw Belt (or by hand) are preserved through a rotation – only the coordinates and velocity change.
See also: Draw Belt, Add/Edit Layers, Faces, Vertices, Move a Layer, Copy and Scale Layer.