Step 1 Cut the Carpet (for Floors Requiring a Carpet Seam)
Put the two pieces of carpet in the room, overlapping them by about 4 inches (4") with enough carpet to reach the walls with an extra 3 inches (3") on all sides. Snap a chalk line on the back of one piece to mark the location of the seam. Cut along the line with a carpet knife guided by a straightedge.
Overlap the edges again. Double check that you still have enough carpet at the wall. Guide a row cutter against the edge you cut. The knife in the cutter will cut the other piece of carpet, creating two perfectly matched pieces.