The main difference between manholes and handholes is just the size of the hole. The so-called manholes are inspection holes set on the pipeline or shaft of a communication system, where this hole can accommodate a person to pass through (either by crawling in or out) during inspections or maintenance of such equipment. In contrast, handholes, being smaller, only allow hands to be inserted for inspection or operation. Moreover, both manholes and handholes are not only required in communication engineering but also in systems like air conditioning (mainly central air conditioning) and power line systems, where such inspection openings are also provided.