The application describes a frame assembly comprising: a first inner frame section adapted to be fitted to a first peripheral portion of a first surface of sheet material, the first peripheral portion is adjacent a peripheral edge; a second, separate inner frame section adapted to be fitted to a second peripheral portion of a second surface of sheet material, the second peripheral portion is adjacent a peripheral edge, and the second surface is opposite the first surface; and an outer frame section for receiving the sheet material with the inner frame sections fitted thereto, the outer frame section comprising first and second projections. The first frame section defines a space adapted to receive the first projection of the outer frame section, the space of the first inner frame section cooperates with the received first projection to restrict movement of the first inner frame section relative to the outer frame section.