A sub-inspection is a segment of the inspection that contains tests specific to it.
For example, if your inspection is for a boat, you might see a sub-inspection for each major area of the boat that is inspected. There might be an electrical sub-inspection, upholstery sub-inspection, hull sub-inspection, and so forth. Within each of these sub-inspections, there are tests relative to each for the inspector to perform.
Each sub-inspection and the tests it contains display on a single page when the inspection is run, as in this example for a PC Collect inspection (Fig. 1):
Fig. 1