The main difference between manholes and handholes is simply the size of the hole. A manhole is a inspection opening installed on the pipeline or manhole of a communication system, which can accommodate a person to pass through (either by crawling in or out) during inspections or maintenance of such equipment. In contrast, a handhole is smaller and only allows hands to be inserted for inspection or operation. Additionally, both manholes and handholes are not only required in communication engineering but also in large-scale systems such as HVAC (mainly central air conditioning) systems and power line systems, where such inspection openings are also provided.