Similar to their brethren, these arbalest -wielding footmen live up to their name, Sappers. They are unstoppable siege machines and using their crossbows, they use the deadly accuracy the crossbow provides to pick off enemies, striking fear in the hearts of those facing them. Although not always carrying shields, all of them do carry the claymore and wield them with skill. Even on the field, they are effective in both close and ranged combat. Like their peers, they are powerful but slow and are easy picking for cavalry and even archers and sharpshooters are able to tear apart the shieldless sappers at a distance with a volley of missles.
That isn't to say they can't take a beating however, and when used in large numbers a few vollies from these deadly marksmen can even reduce a heavy cavalry charge to a handful of men charging on badly injured warhorses, to say nothing of what a large group can do to most armies' mid-to-low tier infantrymen and light cavalry. However fielding such large formations of these intimidating men can quickly burn through the denars in one's purse, with a sapper costing ten denars more to field than a heavy footman and 60 of them easily costing you a couple thousand denars per week.
In 3.9.2, this unit was replaced for the Barclay Janissary.