In spanking, clenching means to close the bottom cheeks by tightening the gluteal muscles. The pelvis is pushed forward, and the cheeks become hard and will lead to the formation of two depressions between the hips and bottom cheeks.
 Means against clenching
Clenching is a common reaction by spankees when they are being spanked. While a minimal amount of clenching can serve as nice visual feedback for the spanker, continuous clenching is usually undesirable because of two reasons: it is perceived as an act of resistance by the spankee (hinting that the spankee is not truly submissive and apologetic, if the spanking is meant to be disciplinary); a clenched bottom is less spankable than a relaxed one. As such, spankers will often either explicitly tell spankees not to clench, or choose a spanking position that makes it difficult for the spankee to clench.
Spanking positions in which clenching is difficult:
- Any position in which the spankee's legs are at an angle to the torso. In other words, this can refer to almost every position except the standing position and the lying position.
- Any position in which the spankee's legs are spread apart, such as the straddling position or over a birching horse.
Other methods to prevent clenching:
- Verbal instruction
- Making the spankee have his/her heels pointing outward and toes pointing inward
- Placing a pile of cushions, pillows, or a bolster under the spankee's hips in a lying position
 Disadvantages of clenching for the spankee
For a spankee, clenching the bottom cheeks during a spanking does not necessarily make the spanks hurt less, contrary to what a spankee might think when he/she is being spanked. Some people say that clenching results in the spanking becoming more painful because flexed muscles receive more damage to the pain-sensitive skin layers and are less able to absorb the impact of the blow as compared to relaxed muscles.