An engineering droid was one of the five major subgroups of second-degree droid, along with astromech droids, environmental droids, exploration droids, and sophisticated repair droids. They differed from their first-degree counterparts, the biological science droids and physical science droids, in that engineering droids worked in applied sciences, using their knowledge to solve real-world engineering and technical problems. Engineering droids worked in a variety of applied sciences, but performed poorly if forced to undertake a different job than the one they were programmed for.