If leaks are likely to be a problem, the slit can be closed off in one of two ways. A flap may be sewn to one side of the slit and a Velcro closure used to secure its other side. And, if necessary, a twist lock fastener and a tab can be added to securely link the ends of the slit together. See Figure 1.

Or the slit can be closed off with a zipper. Since there is no extra material to provide for the zipper installation, we recommend cutting two 2-inch wide lengths of tape (any piece of fabric which is slit is called a tape) from the scrap bimini fabric. Make them three or four inches longer than the slits. This length can include the sleeve or not depending upon personal preference, but stitches in the sleeve assembly will have to be ripped for a few inches in order to secure the zipper tapes.

Attach a zipper half to one edge of one tape so the teeth face in and the zipper tape is flush with one long edge of the fabric tape (see step 1). Then fold the assembly over so the zipper teeth are even with the folded edge of the tape and sew this hem in place (see step 2). Do the same with the other zipper half. These tape assemblies, when complete, are attached to each side of the slit with the zipper teeth up and away from the slit edge — in other words, the tapes are sewn with their raw edges flush with the slit edges and the zipper teeth up (see step 3). Now, fold the tapes over and under so the zipper teeth are matched up opposite one another under the cover (see step 4). Before sewing, zip up the zipper and press the assembly flat . Place a topstitch through the final hems to hold them in place. At the apex of the slit a triangle of leather or vinyl or acrylic can be used to finish the cut and to provide a useful pull tab as well (see step 5).

In some cases (especially with widely spaced double backstays), it may be better to cut openings into the sides of the finished Bimini top (parallel to the aft sleeve assembly). Because side openings are under stress they should be closed off with zippers not flaps. Start the zipper at the edge so that it closes last at the opening for the backstay.