Billet

   A subordinary in the form of an oblong in pale, sometimes showing the thickness but more often with a flat surface. It has sometimes been confused with the delf  which, when oblong in shape, is always borne in fess.

Although the billet is a very common bearing, various opinions have been formed as to what they are intended to represent. Guillim supposes it to be a billet-doux, others a brick, and Sir George Mackenzie, in his Science of Heraldry, oddly suggests that many English families settled in France bore them to denote their extraction from England, as a reminder of the brick used in construction of English houses forgetting that bricks are likewise used in France. Colombiere mentions briques or bricks, as well as billets, and points out the difference between them, the one called briques, being drawn so as to show their thickness, and billets, only flat surfaces, which accords with the idea of their being intended to represent billet-doux for a letter or folded paper, as the French word implies. Gibbon uses the word plinthides.