Skinfold measurement is one technique for estimating body composition.
Take measurements on the right side of the body. Pinch the fold up so that no muscular tissue is included, but don’t pinch too hard. Hold the calipers perpendicular to the fold and measure the skinfold about a quarter of an inch below your fingers.
There are five skinfold sites used for the lab in your text:
For the chest skinfold: Pinch a diagonal fold halfway between the nipple and shoulder crease.
For the abdominal skinfold: Pinch a vertical fold about 1 inch to the right of the navel.
For the thigh skinfold: Pinch a vertical fold midway between the top of the hipbone and the kneecap.
For the triceps skinfold: Pinch a vertical fold on the back of the arm midway between the shoulder and elbow.
For the suprailium skinfold: Pinch a slightly diagonal fold at the top front of the hipbone.