Selected left ribs and spars for horizontal stab and clecoed together. Drilled rib to spar attach holes per instructions. Clecoed HS801PP skin. Prepared and fitted HS404 and HS 405 ribs per instructions and drilled holes in flanges using skin as a guide. Drilled skin attach holes in fwd spar. Drilled remaining holes for HS-405 and HS-404 which included holes for HS-811-1 and HS-814-1.