A system having a joinery frame, a flat filler and a sliding leaf, the joinery frame including a window or door frame having two posts (6, 7), a lower crosspiece and an upper crosspiece, supporting the flat filler including at least one plate made of glass or another material, - said flat filler forming a fixed leaf extending between the upper and lower crosspieces of the frame, - said sliding leaf being slidably mounted between said upper and lower crosspieces, therein or on top thereof, characterised in that: - the frame posts (6, 7) each have: - a first longitudinal cavity opening into a first aperture on the face of the frame post (6, 7) facing the filler, respectively, the sliding leaf, the width of the first aperture being at least equal to the cross-sectional width of the corresponding peripheral edge of the filler, respectively, the sliding leaf and - at least one first rib protruding from the bottom of the first cavity located opposite the first aperture, this first rib extending toward the first aperture over a length which is a fraction of the space between the bottom and the first aperture, - on at least one of the vertical peripheral edges of the filler, the latter is provided with a post having: - a second longitudinal cavity opening into a second aperture located in the first aperture, whose width is at least equal to the cross-sectional width of the corresponding peripheral edge of the filler plate, - means for rigidly fixing the filler plate on its two opposite faces (26a, 26b), located on both sides of the second aperture and directed inward, - the frame post and the filler post having means for rigidly fixing the latter on and entirely within the former which are, for the frame post, located on both sides of the first aperture and directed inward, and for the filler post, located on both sides of the second aperture and directed outward, and - the sliding leaf post being located entirely within a post of the frame in closed position. - said flat filler forming a fixed leaf extending between the upper and lower crosspieces of the frame, - said sliding leaf being slidably mounted between said upper and lower crosspieces, therein or on top thereof, - the frame posts (6, 7) each have: - a first longitudinal cavity opening into a first aperture on the face of the frame post (6, 7) facing the filler, respectively, the sliding leaf, the width of the first aperture being at least equal to the cross-sectional width of the corresponding peripheral edge of the filler, respectively, the sliding leaf and - at least one first rib protruding from the bottom of the first cavity located opposite the first aperture, this first rib extending toward the first aperture over a length which is a fraction of the space between the bottom and the first aperture, - a first longitudinal cavity opening into a first aperture on the face of the frame post (6, 7) facing the filler, respectively, the sliding leaf, the width of the first aperture being at least equal to the cross-sectional width of the corresponding peripheral edge of the filler, respectively, the sliding leaf and - at least one first rib protruding from the bottom of the first cavity located opposite the first aperture, this first rib extending toward the first aperture over a length which is a fraction of the space between the bottom and the first aperture, - on at least one of the vertical peripheral edges of the filler, the latter is provided with a post having: - a second longitudinal cavity opening into a second aperture located in the first aperture, whose width is at least equal to the cross-sectional width of the corresponding peripheral edge of the filler plate, - means for rigidly fixing the filler plate on its two opposite faces (26a, 26b), located on both sides of the second aperture and directed inward, - a second longitudinal cavity opening into a second aperture located in the first aperture, whose width is at least equal to the cross-sectional width of the corresponding peripheral edge of the filler plate, - means for rigidly fixing the filler plate on its two opposite faces (26a, 26b), located on both sides of the second aperture and directed inward, - the frame post and the filler post having means for rigidly fixing the latter on and entirely within the former which are, for the frame post, located on both sides of the first aperture and directed inward, and for the filler post, located on both sides of the second aperture and directed outward, and - the sliding leaf post being located entirely within a post of the frame in closed position.