Definition
Add reps inside a rep range first; when every set reaches the top of the range, add weight and start again at the bottom.
Example: 3 sets of 8 to 12 at 60 kg. Week one the client gets 12, 10 and 9. The weight stays at 60 until all three sets hit 12; then it goes to 62.5 and the reps drop back toward 8.
It suits exercises where the smallest weight jump is a big one, which is most dumbbell and cable work, and it regulates itself: a tired week just means fewer reps, not a failed session.
Two rules keep it honest. Every set uses the same weight, and only clean reps count. If a client stalls for three weeks at the same reps, widen the range or change the exercise.