Like the ovolo, the torus and the bead are simple convex mouldings, the difference being that where the ovolo is the arc of a quarter-circle, the torus and bead are arcs of semi-circles. They are often flanked above and below by fillets, which give them better definition and prevent the shadows they cast from obscuring the transition from bead to the underlying wall plane.

The distinction between torus and bead, like that between fascia and fillet, is only one of scale: when the profile is thick in relation to the overall composition, it is known as a torus; when thin, it is called a bead (or sometimes an astragal, especially if ornamented). Multiple beads arrayed side by side are known as reeding.

Beads and torii often serve the same auxilliary role as fillets and fascia, and could in fact be considered an extreme kind of ‘rounded fillet’, where the edges of the fillet are radiused to the point that the flat ‘face’ disappears as the rounded edges meet in the middle. The shadow gradient of a torus or bead is a smooth transition from full highlight at the top to full shadow at the base; these profiles produce a richer and more subtle effect than the sharp orthogonal contrasts of the flat-faced fillet and fascia.

Whereas the bead, like the fillet, is considered to be a separating moulding, the wider torus is a binding moulding: it acts to span the elements above and below it rather than severing them.

As convex mouldings, the bead and torus are robust and ‘forward’ in nature, and if over-used or over-sized in a composition can result in a crude or overpowering effect. They are more often seen at the bottom of compositions than at the top, and are usually employed in a supporting rather than a starring role.

A wide fascia topped with a bead is a common choice of profile for skirting boards, and weatherboards beaded along their lower edge can still occasionally be seen on colonial era houses in Australia.

A skirting board consisting of a fascia and bead, separated by a channel (sunk fillet)

The torus is a distinctive feature of the bases of classical columns (the exception being the baseless Doric order), where the bulge of the profile perfectly expresses the work being done by the base of the column in bearing its load, seeming almost to deform in the process. One theory on the origin of the torus in this application is that it represents the ropes once used to tie sacrificial victims to sacred trees, an account that sounds more fanciful than factual.