A scalloped top is cut into the pickets, not into the fence. Every rail on a scalloped timber picket fence stays dead level, the same as a flat-top fence; what changes is the length of each picket, cut shorter toward the middle of the span so the row of picket tips traces a smooth concave dip, or longer toward the middle for a convex arch. The two end pickets at every post or panel boundary always land back at the full entered height, so the classic scalloped silhouette repeats cleanly bay to bay along a fence run.
Because no two pickets in a scalloped run share exactly the same cut length, a scalloped fence or gate needs its own "Picket Lengths" schedule on the drawing, grouping pickets by their measured length rather than calling out one cut-length note the way a flat-top fence can. On a scalloped double-swing gate each leaf dips independently over its own span and returns to full height at both the hinge post and the meeting stile, so the gate reads as two mirrored dips either side of the centre line rather than one continuous sweep across the whole opening.
Concave (dipped) is the classic scalloped picket fence look; convex (arched) reads as an arched top instead. Both directions are set by a single depth measured down or up from the entered height at the centre of the span, and CAD60 clamps that depth against the picket head height so the top rail can never be driven into the shortest picket's shoulder.