Vibration dampeners are placed or woven between the main strings of a racquet’s stringbed outside of the cross strings of a tennis racquet.
There are two key reasons for this placement. First, when you’re hitting, you don’t want the tennis ball to accidentally come in contact with the vibration dampener and lead to a mishit.
However, the second and lesser-known reason for this particular placement is that it’s in the rules.
In section 4 of the ITF Rules of Tennis, the use of vibration dampeners is address head-on as a part of five common cases they encounter:
Case 3: Can vibration damping devices be placed on the strings of a racket? If so, where can they be placed?
Decision: Yes, but these devices may only be placed outside the pattern of the crossed strings.
That means you can place dampeners on the bottom, top, left, or right, of the stringbed. Of course, back to reason one, players typically place them at the bottom of the stringbed above the racquet’s throat to prevent them from interfering when hitting.
It’s worth noting that the rules don’t explicitly prevent players from using multiple vibration dampeners as long as they don’t violate the above rule. Still, it’s entirely unnecessary to do so.