A leaf, of a sliding window or sliding door, has a top profile that is provided with at least one hardware component and which has a side profile perpendicular to the top profile, whereby the top of the top profile has a groove with undercut flanks extending in the longitudinal direction of the top profile, whereby the hardware component or hardware components is or are fastened to a first part of a connecting piece, whereby the first part has a shape that is at least partly complementary to the groove, the first part being held in the groove and locked in the longitudinal direction of the groove.