The opening for the Trofast has to be cut big enough to slide the unit in. A thin cutoff wheel (1/16") on a die grinder or angle head grinder will also work. It is a very messy job, remember
fiberglass dust is dangerous. I add a taller Trofast to a
Scamp 16 closet. After it was inserted I secured it in the closet with screws from the outside. Spacers had to be installed between the Trofast and the inside of the closet to line it up in the opening. I then trimmed the opening with scribed furring strips to fill the front of the closet
fiberglass. Also I built new double doors, so that when opened the doors would not block the aisle.