This refers to the parts of a rifle: Lock, such as Flintlock; stock as the wooden stock and the rifle barrel. So, if you bought something lock, stock and barrel, that meant that he accepted the whole thing or the whole story and not just a part of it.
Traditionally they were the lock, the stock, and the barrel. This was also the origin of the expression that meant "the whole thing".
Lock stock and barrel
Lock, stock, barrel
Taditionally, this was the "lock, stock, and barrel". The stock or grips permits the shooter to hold the gun, the barrel guides the projectiles. The lock, or action, controls the firing of the cartridge or charge. Lock, stock and barrel has become a phrase meaning the entire thing.
You made the barrel, fitted the stock to the barrel, then fitted the lock to the stock.
Lock, stock, barrel
Lock, Stock, Barrel
Lock, stock and barrel. Lock holds the firing mechanism, stock gives you something to hold onto, barrel spins the projectile.
Lock, stock and barrel
Lock, stock, and barrel
Lock, stock and barrel
hook, line and sinker; lock, stock and barrel