Crossbows were initially drawn by hand, by placing ones foot in the triangular
stirrup-like thing in front of the bow, grabbing the
string with straight arms and straightening the leg (Another option was to attach the string to a hook on the belt), but after the introduction of the
steel bow (which replaced the bows made from
wood,
sinews or
horn, often by laminating different materials) around
1400, the increased
draw-weight made this impossible, and a
lever or
cranequin had to be used.
In 1139, pope Innocentius II declared the use of a crossbow against fellow (or not-so-fellow, one might presume) christians a crime, but since almost everyone (except perhaps the Welsh) had realised the advantage of the crossbow over the longbow - the flatter trajectory made aiming easier, no one paid much attention to the pope in this matter.
The ammunition used by crossbows is called bolts or quarrels.