BILLET, in England is a ticket for quartering soldiers, which intitles each soldier, by act of parliament, to candles, vinegar, and salt, with the use of fire, and the necessary utensils for dressing and eating their meat. The allowance of small beer has been added by a late regulation. BILLET _de logement_, _Fr._ a billet for quarters. This billet or ticket was formerly delivered out to the French troops upon the same general principles that it is issued in England. BILLETING, in the army, implies the quartering soldiers in the houses of any town or village. BINACLE, a telescope with 2 tubes, so constructed, that a distant object might be seen with both eyes, now rarely used. BIVOUAC, BIOUAC, BIOUVAC, or BIOVAC, _Fr._ [from the German _weywacht_, a double watch or guard.] A night-guard, or a detachment of the whole army, which during a siege, or in the presence of an enemy, marches out every night in squadrons or battalions to line the circumvallations, or to take post in front of the camp, for the purpose of securing their quarters, preventing surprises, and of obstructing supplies. When an army does not encamp, but lies under arms all night, it is said to _bivoac_. Thus before the battle of Austerlitz, Bonaparte was all night in _bivoac_, or with the advanced guard. BIT, the bridle of a horse, which acts by the assistance of a curb. See CURB and BRIDON. BLACK-HOLE, a place of confinement for soldiers, in the English discipline, who may be confined therein by the commanding officer, but not by any inferior officer. In this place they are generally restricted to bread and water. BLANKETS, are made of coarse paper steeped in a solution of saltpetre, and when dry are again dipt in a composition of tallow, resin, and sulphur. They are used only in fire-ships. BLAST, and BLASTING. See MINE and MINING. BLINDS, in military affairs, are wooden frames, composed of 4 pieces, either flat or round, two of which are 6 feet long, and the others 3 or 4 feet, which serve as spars to fasten the two first together: the longest are pointed at both ends, and the two others are fastened towards the extremities of the former, at about 10 or 12 inches from their points, the whole forming a rectangular parallelogram, the long sides of which project beyond the other about 10 or 12 inches. Their use is to fix them either upright, or in a vertical position, against the sides of the trenches or saps, to sustain the earth. Their points at the bottom serve to fix them in the earth, and those at top to hold the fascines that are placed upon them; so that the sap or trench is formed into a kind of covered gallery, to secure the troops from stones and grenades. The term _Blind_ is also used to express a kind of hurdle, made of the branches of trees, behind which the soldiers, miners, or labourers, may carry on their work without being seen. See HURDLE.