The terminology is that the brick laying guy is a "builder" and the exploding guy is not actually a job - you're just killing him. (Then "exploder" is a job in Lemmings 2.)
In Lemmings 2 it was an important mechanic that blockers would stop blocking if you removed the ground underneath them, since by doing that you'd get credit for saving them instead of killing them. It tended to defeat the concept of the blocker, but I suspect the same was true in the original.
