Da, big; du, assembling. The point is at the big toe, where the Qi of meridian gathers.
On the medial side of the big toe, distal and inferior to the 1st metatarsophalangeal joint, at the junction of the red and white skin.
Stomachache, constipation, diarrhea, fever without sweating.
Perpendicularly 0.3-0.5 cun.