A structure for sliding architectural elements, comprising: - an in-wall frame which is shaped substantially like a parallelepiped and comprises a first vertical main face and a second vertical main face which are mutually parallel and opposite, an open passage face which is vertical and perpendicular to said main faces (11, 12), a horizontal upper face and a horizontal lower base, at least said main faces (11, 12) comprising a plurality of vertical posts (20, 30, 23, 24) adapted to connect said upper face to said lower base, - a sliding body, which can slide within said in-wall frame and through said open passage face, parallel to said first main face and said second main face along a horizontal sliding axis, between a retracted position, in which it is mostly included inside said in-wall frame, and an extracted position, in which it mostly protrudes outside of said in-wall frame from said open face, wherein said in-wall frame comprises, on said upper face, a horizontal sliding guide which is integral therewith and said sliding body comprises a sliding carriage which can slide along said horizontal sliding guide, said sliding carriage being adapted to support a sliding door or a sliding panel or the like, said upper face and said lower base are provided with a plurality of transverse pre-cutting incisions which renders said upper face and said lower base breakable along preset transverse axes so as to reduce the depth and/or width of said in-wall frame, characterized in that said lower base comprises two lateral longitudinal components which are fixed parallel to each other and are spaced by means of at least two connecting plates which interlock in respective contoured recesses with which each one of said longitudinal lateral components is provided; said connecting plates being provided with longitudinal pre-cutting incisions which render said connecting plates breakable along preset longitudinal axes so as to reduce the width of said lower base, and in that said upper face comprises upper central plates to the edges of which two longitudinal lateral profiles are coupled and said upper central plates are provided with longitudinal precutting incisions, by means of which it is possible to break them along preset cutting axes so as to vary the distance between the two longitudinal lateral profiles, so as to move them closer in order to reduce the width of the upper face. - an in-wall frame which is shaped substantially like a parallelepiped and comprises a first vertical main face and a second vertical main face which are mutually parallel and opposite, an open passage face which is vertical and perpendicular to said main faces (11, 12), a horizontal upper face and a horizontal lower base, at least said main faces (11, 12) comprising a plurality of vertical posts (20, 30, 23, 24) adapted to connect said upper face to said lower base, - a sliding body, which can slide within said in-wall frame and through said open passage face, parallel to said first main face and said second main face along a horizontal sliding axis, between a retracted position, in which it is mostly included inside said in-wall frame, and an extracted position, in which it mostly protrudes outside of said in-wall frame from said open face, said in-wall frame comprises, on said upper face, a horizontal sliding guide which is integral therewith and said sliding body comprises a sliding carriage which can slide along said horizontal sliding guide, said sliding carriage being adapted to support a sliding door or a sliding panel or the like, said upper face and said lower base are provided with a plurality of transverse pre-cutting incisions which renders said upper face and said lower base breakable along preset transverse axes so as to reduce the depth and/or width of said in-wall frame, characterized in that said lower base comprises two lateral longitudinal components which are fixed parallel to each other and are spaced by means of at least two connecting plates which interlock in respective contoured recesses with which each one of said longitudinal lateral components is provided; said connecting plates being provided with longitudinal pre-cutting incisions which render said connecting plates breakable along preset longitudinal axes so as to reduce the width of said lower base, and in that said upper face comprises upper central plates to the edges of which two longitudinal lateral profiles are coupled and said upper central plates are provided with longitudinal precutting incisions, by means of which it is possible to break them along preset cutting axes so as to vary the distance between the two longitudinal lateral profiles, so as to move them closer in order to reduce the width of the upper face.