Pit being a three letter word, doesn't search well on the forum, however, using Google you can search just GJ. Enter the following in google.........
site:garagejournal.com/forum pit
Will bring up everything pit, from pit bulls to holes in the floor to pit maneuvers, however, as noted, this is a often asked question, probably once a month on average.
With todays front wheel drive cars, there is very little to access under a car that the average home mechanic might work on. A fuel filter, a O2 sensor and the oil drain plug, not much more that you can do from a pit. To be safe and functional, a pit needs easy access (ingress/egress by the user) with the vehicle in place on it, it needs forced air ventilation, it needs properly sealed, explosion proof electrical devices and light fixtures, drainage to prevent it from flooding, and a way to cover it to make the garage floor safe and usable for other things when the pit is not in use. Many locales do not allow pits. Thats all I'm going to say on the matter....... As Baz noted it can become a hotly debated topic.
Charles