Sash for closing an architectural opening, comprising: i) weight-bearing frame, placed towards the inside, preferably in wood; ii) at least one transparent element, preferably of a planar shape, suitable to allow the passage of light through the sash, housed on, and supported by, the weight-bearing frame; iii) a cover frame, placed towards the outside, preferably in aluminium, fitted on the weight-bearing frame, suitable to protect the latter on the outer side; wherein the cover frame comprises: n) a structure comprising upright elements and transversal elements suitable to engage each other perpendicularly, wherein which the upright element identifies, along its extension, an upright cavity and/or an upright groove (410") and the transversal element identifies, along its extension, a transversal cavity; m) a plurality of locking elements, each locking element is made in one piece and comprises: - an upright portion comprising a locking lip suitable to be housed, with a transverse insertion, in the upright groove (410"); characterised in that each locking element further comprises: - a transversal portion suitable to be snap-engaged, with a rotation of the locking element, in the transversal cavity of the transversal element; and wherein the upright portion and transversal portion are mutually interacting in such a way that the snap-engagement between the transversal portion and transversal element reached by the rotation of the locking element, transmits an action to the locking lip that engages the walls of the upright groove (410") wherein is housed and that forcibly locks the upright element to the transversal element. i) weight-bearing frame, placed towards the inside, preferably in wood; ii) at least one transparent element, preferably of a planar shape, suitable to allow the passage of light through the sash, housed on, and supported by, the weight-bearing frame; iii) a cover frame, placed towards the outside, preferably in aluminium, fitted on the weight-bearing frame, suitable to protect the latter on the outer side; n) a structure comprising upright elements and transversal elements suitable to engage each other perpendicularly, wherein which the upright element identifies, along its extension, an upright cavity and/or an upright groove (410") and the transversal element identifies, along its extension, a transversal cavity; m) a plurality of locking elements, each locking element is made in one piece and comprises: - an upright portion comprising a locking lip suitable to be housed, with a transverse insertion, in the upright groove (410"); characterised in that each locking element further comprises: - a transversal portion suitable to be snap-engaged, with a rotation of the locking element, in the transversal cavity of the transversal element; and - an upright portion comprising a locking lip suitable to be housed, with a transverse insertion, in the upright groove (410"); characterised in that each locking element further comprises: - a transversal portion suitable to be snap-engaged, with a rotation of the locking element, in the transversal cavity of the transversal element; and - a transversal portion suitable to be snap-engaged, with a rotation of the locking element, in the transversal cavity of the transversal element; and