An access point was a connection between corridors and decks with maintenance shafts and Jefferies tubes aboard a starship.
In 2153, Captain Jonathan Archer ordered to post security guards at every access point aboard Enterprise NX-01 to locate the Tarkaleans. (ENT: "Regeneration")
When the Borg took over control of the USS Enterprise-E in 2373, Captain Jean-Luc Picard orderd to seal off deck 16 and post security teams at every access point. (Star Trek: First Contact)
The same year, Miles O'Brien found an access point into the crashed Jem'Hadar attack ship. (DS9: "The Ship")
Also in 2373, Captain Kathryn Janeway ordered to post security details at every access point and confine the Nygeans to the cargo bays. (VOY: "Displaced")
When the Borg took over the USS Voyager in 2373, Chakotay sealed off decks 9 through 13 and posted security details at every access point. (VOY: "Scorpion")
When Captain Braxton beamed aboard the Voyager, Captain Janeway ordered Starfleet Security to deck 4 section 12 and to errect force fields around all access points. (VOY: "Relativity")