Drawing: the blue rectangle is your pattern tile — everything repeats with it. Draw with L line, P polyline (double-click / Enter to finish, Esc cancels), R rectangle, C circle, F freehand for organic shapes. Hold Shift for ortho. G grid snap, E endpoint snap. Tracing: load a PDF or image underlay, use Calibrate scale (click two points on the underlay, type the real distance), then trace over it. Seamless: the faint ghost copies around the tile show exactly how the pattern repeats. Check seamless finds problems; Make seamless wraps anything crossing the tile edge to the opposite side so the tile repeats perfectly. Export: pick Model and/or Drafting, then Export .PAT. In Revit: Manage → Additional Settings → Fill Patterns → New → Custom → Import.