A pleasant menagerie of words grazes in the field of architectural mouldings (the projecting or incised bands that serve useful and aesthetic purposes): gadroon, astragal, larmier and rabbet, but none is chunkier or more mysterious than bolection.
Bolection mouldings cover joints, especially between surfaces of different levels, such as round the panels of a door. Such three-dimensional things are hard to describe clearly in words.
No one knows the origin of bolection and even its proper form is uncertain: balection, belection, bilection, bolexion. It sounds like the Liberal Democrat attitude to Brexit. Gadroon derives from the name of a round convex fold sewn into a piece of textile, found as goderon in 14th-century French. Christopher Wren wrote of ‘fluting the face of thee great Pillasters with Gadrons’. People usually think of gadroons as convex and fluting as concave, but if the convex and concave parts are of similar proportions, who is to say whether the pattern is raised or incised?
With astragal we reach firm etymological ground. Astragalos is Greek for an ankle-bone, otherwise a huckle-bone, or in Latin talus. The huckle-bones of animals were used as dice in the ancient world. That is not much clue to the form of an astragal moulding, which at its simplest is a convex C-shape in section.
An astragal runs horizontally round the top of a Tuscan pillar below the necking and echinus (the latter being the bulgy part that supports the abacus, echinos being the Greek for a hedgehog or sea urchin, which must have been presumed to bear a likeness to it). Corinthian columns have an astragal too, below the capital where the acanthuses grow. Larmier has a usefully mnemonic derivation from French larme, ‘a tear’, it being a projection on an outdoor cornice letting rain drop clear of the masonry beneath it. It is otherwise known as a drip. Larmier was often spelled lorymner, confusing things, since the surname Lorimer is a maker of parts of a horse’s harness.
As for rabbet (pronounced like the burrowing mammal, even when the more recent spelling rebate is used), space forbids adequate discussion. There’s much to be said. Our subject, after all, is rabbit and pork — talk.