This is a 3 post variation of Roukie68's drill guide that fits my DeWalt DCD780 perfectly. It should also work with the DCD777 as it uses the same dimensions as Roukie68's design. Bar lengths are up to you, although I used 3x 265mm bars.
To assemble it I used a 5/16'' drill bit to drill the holes in the bottom and a 21/64'' bit to drill the mounting holes. Finally, I used a heat gun to heat the ends of the rods and hammer them into the base.
Fusion 360, SketchUp and STEP files are included.
The product was designed by
jhoff