Mechanism for a window, the window comprising a window casement and a window frame, the mechanism is displaceably guidable along parallel guide grooves of the window frame and mounted pivotably 180° and 360° around a horizontal bearing spindle and supported by support arms (29, 30) of the mechanism, which are in use of the mechanism with the window on each side of the casement and the window frame, the mechanism further comprising guiding means and locking means for the window, whereby i) a single handle or another lever coupleable in the frame or casement of the window is connected with said locking means for the window and connected with said guiding means including guide pins for the window, ii) the guide pins comprise paired upper and lower, respectively, guide pins, projecting in the horizontal direction from respective guide frames (11, 12), whereby the guide pins are receivable guidable by the parallel guide grooves in the window frame extending along the window frame, iii) the guide frames (11, 12) are paired half-looped guide frames (11, 12) for manual actuation of said upper or lower pair of guide pins, which pairs of upper and lower guide pins are connected with the guide frame (11, 12) respectively, and in use of the mechanism with the window situated along the casement of said window, whereby the guide frames (11, 12) are counter-directed to each other with their open portions (17, 18), iv) said guide frames (11, 12) are interconnected via a motion connection (21, 22), which upon actuation is alternately arranged to actuate said upper or lower guide pins, in use of the mechanism with the window at the upper and lower, respectively, halves of the window, to allow the turning around of the window during simultaneous guiding by means of the upper or lower paired guide pins respectively, v) and the pair of upper and lower guide pins are horizontally movable and connected with paired bars, which, via said motion (21, 22) connection which is formed of a number of pivotably mounted links, are in use of the mechanism with the window interconnected at the upper and lower, respectively, halves of the window, and received in the guide grooves, for simultaneous parallel motion out and in, respectively, whereby the locking and guiding, respectively, of the window are arranged to be provided by said single handle or lever. i) a single handle or another lever coupleable in the frame or casement of the window is connected with said locking means for the window and connected with said guiding means including guide pins for the window, ii) the guide pins comprise paired upper and lower, respectively, guide pins, projecting in the horizontal direction from respective guide frames (11, 12), whereby the guide pins are receivable guidable by the parallel guide grooves in the window frame extending along the window frame, iii) the guide frames (11, 12) are paired half-looped guide frames (11, 12) for manual actuation of said upper or lower pair of guide pins, which pairs of upper and lower guide pins are connected with the guide frame (11, 12) respectively, and in use of the mechanism with the window situated along the casement of said window, whereby the guide frames (11, 12) are counter-directed to each other with their open portions (17, 18), iv) said guide frames (11, 12) are interconnected via a motion connection (21, 22), which upon actuation is alternately arranged to actuate said upper or lower guide pins, in use of the mechanism with the window at the upper and lower, respectively, halves of the window, to allow the turning around of the window during simultaneous guiding by means of the upper or lower paired guide pins respectively, v) and the pair of upper and lower guide pins are horizontally movable and connected with paired bars, which, via said motion (21, 22) connection which is formed of a number of pivotably mounted links, are in use of the mechanism with the window interconnected at the upper and lower, respectively, halves of the window, and received in the guide grooves, for simultaneous parallel motion out and in, respectively, whereby the locking and guiding, respectively, of the window are arranged to be provided by said single handle or lever.