Workmen are monsters found at the Digsite. They can be pickpocketed by players at level 25 thieving, and only attack when pickpocketing fails.
Pickpocketing does not give the player thieving experience.
They need to be pickpocketed during the Digsite quest in order to obtain one of the rock samples.
Players who wish to obtain multiple Chest keys may do so by simply begging for the key again. You will not be required to drop the key before obtaining another one.
The Digsite Workmen are tan skin toned men who are wearing boots, a black shirt, black pants, a brown apron, and some type of gloves.
This article on a monster has an associated dialogue page.