Mark the "overlap" with colored chalk to establish a "line" for primer/activator and seam tape application.

Use a 3" stiff brush to apply a full coat of primer activator along the "line."  Apply to both sheets, bottom sheet along the mark, and top sheet on the underside overlap area. (Note photo 4.)

Allow the primer activator to "flash off," or become totally dry to the touch, usually about 10-15 minutes in 75 to 85 degree sunny weather. Allow a longer period of time in humid, cool, and or cloudy weather.

Apply 3" seam tape to bottom sheet in an "unroll" fashion, using the opposite hand to press the seam tape into contact with the bottom sheet. Avoid any wrinkles, and make sure to keep the roll taut as you unroll the tape into position on the bottom sheet.

Use a small steel roller to roll the seam tape into GOOD contact with the bottom sheet. Also apply a bead of water cut off (gray color), or lap sealant (black color) about 2 -3 inches from the seam tape on the underside sheet.

Start at the one end of the bottom sheet, and peel up the wax release paper from about 6 inches of the bottom tape, making sure NOT to peel up the 3" seam tape from the bottom sheet, and do not tear off the wax paper. Next, totally "flop" over or fold the top sheet on the bottom sheet so the entire seam area is covered with the top sheet. Next, start "brushing" with your hand the top sheet onto the lower sheet, and at the same time start pulling the wax paper off the tape from the bottom sheet as you are "brushing" the top sheet onto the underside sheet. Continue down the seam the entire sheet in this fashion, pulling the wax paper as you use the brushing motion.

Use lap sealant to seal the finished top edge.