Seamer set for 1-1/2" seam
There are three threaded holes at each corner for positioning the legs. Remove each 1/4-20x5/8 screw and slide the leg down until the holes in the leg align with the bottom two holes. Then reinstall the bolts. When this is done at all four corners the seamer's height is now adjusted.
NOTE: Make sure that all four outrigger legs are set to the same position in order for the seamer to sit properly on the seam.