Adding weight to the grip end of a club — via a heavier grip, a butt plug, or a counterbalanced shaft design — to pull the balance point up toward the hands. The arithmetic is the interesting part: total weight goes up, but swing weight (measured on a fulcrum 14 inches from the grip end) goes down, so the head feels lighter and easier to move. That lets a builder add head mass, play a longer shaft, or steady out handsy tendencies without the club feeling like a sledgehammer. It is most common in putters — where extra hand-end mass quiets the stroke — and in driver builds chasing length. Overdo it and the club feels dead in the hands, so it is a fitting-bay adjustment, not a guess.