The top and bottom tracks supplied by the manufacturer must be cut slightly shorter than
— Use a measuring tape to find the distance from wall to wall along the top edge of the shower base (or tub) and, for the top track, at 6 feet above it.
--Follow the manufacturer’s directions and subtract the required amount for each track from the total width of the opening.
--Cut both tracks to length and smooth any rough edges at the cut end with a fine file.
Use a hacksaw and a miter box to ensure a square cut. Putting a block of scrap wood in the track and clamping helps keep the track square and in place while you cut it. tracks supplied