To keep the cover from being too warm for summer use, make a wide opening at the top, centered on the back, so air can circulate.
Fold under a hem of 3⁄4 in. + 3⁄4 in. around the edge and sew it down, or finish edge with bias tape.
If you didn’t cut out the front blind in the same piece as the top, cut it out separately. The blind should be a little bigger than an air vent; don’t forget the seam allowances. Hem around both short sides and one long side. Sew the other long side securely to the top if it wasn’t previously cut as one piece. Attach Velcro® so that the blind can be held down when it’s cold. Also attach Velcro® on the top so the blind can be held open (see photo). In order to adjust the air vents, use lengths of Velcro® on the top.Use Velcro® or ribbon on the long sides of the air vents to attach the back to the crate.
Sew the sides and back securely to the top (with front and blind) if they were not cut out as a single piece. Sew the back to the sides, with side A at side B.
If you are sewing the sides to the front, match side C to side D. Fold and sew a hem around entire lower edge.
You may also want to sew a Velcro® or ribbon closure on the lower edge at C, if needed.
If there is a carrying handle on the cage, cut out an opening for it in the cover. Overcast the raw edges, then hem or edge with bias tape.