An apparatus for assisting the closing and opening of a lift and slide element such as a lift and slide door or a lift and slide window, said apparatus comprising: - a base body which is configured for attachment to a leaf frame of a lift and slide element; - an axially extending first preloading element, in particular a first gas pressure spring, which has a first end and a second end which is connected in an articulated manner to the base body; - an axially extending second preloading element, in particular a second gas pressure spring, which has a first end and a second end which is connected in an articulated manner to the base body; and - a switchover mechanism comprising a first and a second defined end switching position, via which switchover mechanism the first end of the first preloading element is coupled to the first end of the second preloading element under a preload of the first and/or the second preloading element, characterized in that the switchover mechanism has an unstable equilibrium position between its two end switching positions, with the two preloading elements (54, 56) being aligned with one another only in the unstable equilibrium position; in that the switchover mechanism has a switchover element which is angled in an L shape and which comprises a first and a second limb (72, 74), which are preferably oriented substantially perpendicular to one another, with the first end of the first preloading element being connected in an articulated manner to the free end of the first limb and the first end of the second preloading element being connected in an articulated manner to the free end of the second limb; and in that the switchover mechanism is displaceably supported at the base body and is secured thereat against lifting forces. - a base body which is configured for attachment to a leaf frame of a lift and slide element; - an axially extending first preloading element, in particular a first gas pressure spring, which has a first end and a second end which is connected in an articulated manner to the base body; - an axially extending second preloading element, in particular a second gas pressure spring, which has a first end and a second end which is connected in an articulated manner to the base body; and - a switchover mechanism comprising a first and a second defined end switching position, via which switchover mechanism the first end of the first preloading element is coupled to the first end of the second preloading element under a preload of the first and/or the second preloading element, the switchover mechanism has an unstable equilibrium position between its two end switching positions, with the two preloading elements (54, 56) being aligned with one another only in the unstable equilibrium position; in that the switchover mechanism has a switchover element which is angled in an L shape and which comprises a first and a second limb (72, 74), which are preferably oriented substantially perpendicular to one another, with the first end of the first preloading element being connected in an articulated manner to the free end of the first limb and the first end of the second preloading element being connected in an articulated manner to the free end of the second limb; and in that the switchover mechanism is displaceably supported at the base body and is secured thereat against lifting forces.