There is only one tool used to adjust the front sight, depending on which version of M16 you have. The earlier M16A1 type had a front sight post that consisted of a round post with five notches in its base. It requires a front sight tool with five "lugs". The current M16A2 style uses a square post with four notches in its base, and requires a similar tool with four lugs.
There is also a tool made that has four lugs on one end, and five on the other for adjusting both kinds of front sights if you have both kinds of rifles. For an A1, there is a tool that has a five lug small-diameter end for the front sight (elevation) and a five lug large-diameter end for the A1 rear sight windage wheel.
To use the tool, whichever one is correct for your rifle, slide it down over the front sight post so that the lugs on the tool fit into the notches. The forward notch will be engaged by a spring loaded detent pin in the front sight base that prevents the post from turning, but the tool will depress that pin, as well as engage in the notches to permit you to turn the post.
Turning to the right screws the post further in to the base, which lowers the post and raises the POI. Turning to the left raises screws the post further out, which lowers the POI. As you turn, kind of ease up on the pressure on the tool, and you will feel the detent re-engage the notch as the sight turns to the next "click".
The military, as far as I know, doesn't issue sight adjusting tools. By using a bullet tip or any other small pointed object, one can depress the detent pin and rotate the front sight as needed. A tool is more convenient, however.