Nipple Trainer
From BME Encyclopedia
A nipple trainer is a specialized form of nipple shield that acts similarly to a nipple stretcher but has a variable height. The height is usually selected by adjustment screws which allow two (or more) plates to be forced different distances apart. While they are commercially available, due to the simplicity of the design the vast majority of nipple trainers tend to be homemade (as in the pictures below).
Similar devices exist for scrotal stretching and penis stretching.