Main designators used daily by FACs and other fliers at NKP represented locations of key intersections and interdiction points. There were eight interdiction points assigned the phonetic alphabet letters of ALPHA through HOTEL. ALPHA through GOLF were on Routes 911 and 91; and HOTEL was on Route 912, a new road built in 1966. Some of the most hotly contested road segments on the Laotian portion of the Ho Chi Minh Trail were among these eight points.
In the FAC jargon, ALPHA, BRAVO and CHARLIE became known as the Chokes. The Chokes were surrounded by one of the deadliest concentrations of AAA/AW between the Mu Gia Pass-Dog House area and the heavily defended transhipment area at Tchepone.