Assembling of the frame through internal squares for angles and joints for lateral parts, in the most important formats for which frames are cut in half or in more pieces in order to easily assemble and disassemble the structure. Frame in aluminium varnished with matt black epoxy powders. The structure, particularly suitable for back screen projections, offers the possibility to be widened by adding frame parts, in case the screen must be enlarged, using the same basic structure. It is possible to equip the structure with a pair of steel “T” uprights for screens up to format 400 x 300 cm. The screens are realized with (standard) fireproof, washable, professional white fabric, and upon request, with other fabrics for front and back screen projections such to satisfy all particular projection needs.