2 bubble levels in the sky-screen rail, a 15' long piece of string with 2 beads on it, a felt marker pen & a tripod with a gear-driven center column. One bubble level is left-right, for horizontal leveling, the other is front-rear for directional leveling.
OK here's how.
To set up the first time:
Level the rail front to back & sideways with the tripod's head adjustments.
Wind up the center column about 1/2 way.
Raise/lower the leg sections till the center of the swept area is aligned with the bore of the unloaded, benched gun. Do this with the "START" screen 3"~4" yes INCHES in front of the muzzle.
Mark the leg extension with the sharpie. (That way you can re-create the height without doing all this messing about again)
Trail the string till the bead tied to the string at 10 or 15 feet (your choice) is touching the muzzle. Measure to the center of the sky-screen rail.
Tie the end of the string to the rail.
*set the target up wherever you want to shoot for group at this point*
Wind the center column up/down till the center "sweet spot" is in line with the muzzle & the bullseye.
Mark the center column extension used.
You're done.
To re use:
Set all the leg extensions to the marks, set the column extension to the mark.
Level the rail.
Run out the length of string till the bead of choice touches the muzzle.
