Hello Claire, a sapper is a job in the Commonwealth military, same rank as private. The lowest rank of military engineers or royal engineers. Military engineers do combat engineering, construction, penetrating minefields, disarming booby traps, building roads and bridges and so forth. Truthfully I am not a sapper, I am an officer in the Canadian Air Command. My maternal granddad was a Royal Canadian Engineer and I was very attached to him as a kid, hence the name.