Section shapes.

section shapes

L-R: Pinched, Pinched, Wide Lip, Narrow Lip, Tapered, Straight.

Tapered Sections. The taper can be quite sharp or not.

Straight Sections.

Pinched Sections. The pinch can be subtle or deep.

Lipped Sections. Straight with lip, pinched with lip, and very slight taper – almost straight – with lip.