A baluster whose upper half has the same profile as the lower half.

Two beads, side by side; there is no other surface or molding between them.

An ax having a two-edged blade.

Two L-shaped metal structural members which are fastened together, back to back.

A reciprocal pump in which the reciprocating motion of a piston does work in both directions.

A hinge which permits motion in either of two directions; used on swinging doors.