A direct thrust performed from a contact distance. The term stich is used in several different contexts, and seems to be synonymous to latin word fixura, which is also used in I.33.
In play 23, stich seems to be connected to cavazione-like motion that escapes from the opponent's rebind and hits him. But this is not true in other contexts, so we cannot say that stich is the same as cavazione. Rather, cavazione is one of several actions that can be described as a stich in the priest's terminology.