A pet-door assembly and method of use includes providing a pet-door assembly with a body having a first end, a second end, and a length separating the first end from the second end, a securing member coupled at the second end of the body, the securing member having a first end and a second end, the first end and the second end being shaped to fit within and engage a frame of a sliding door, and a plurality of strips each having a first end, a second end, and a length separating the first end from the second end, the first end of the plurality of strips coupled to the securing member and the length of the plurality of strips being less than half the length of the body. The method further includes the step of mechanically fixing the pet door in overlapping relation with an opening in a wall, the opening having a horizontally-sliding door disposed. within, the horizontally-sliding door having a first position that obstructs the opening and a second position that leaves at least a portion of the opening overlapped by the pet door unobstructed.
