Measuring skin folds is a method of estimating body fat that requires the use of a trained pincher, a skin fold caliper, a measuring tape as well as marker. Measuring skin folds only require a select few parts of the body, namely the triceps, pectoral, subscapula, midaxilla, abdomen, suprailiac and the quadriceps.
This is done by having the pincher only pinch the skin and fat of these areas without holding onto any muscle. The measuring tape and marker are used in this process to help locate the area to pinch, some places even requiring to pinch at certain angles. Afterwards the skin fold caliper is used to measure the thickness of the skin fold in millimetres. The thickness is then measured a few more times and then averaged to be accurate. These values would then be used in a formula, which varies depending on the person, to measure the percent of fat in the body.
This is an example of measuring skin folds: http://www.youtube.com/watch?v=4qRoISff5Cs