An interlocking device for interlocking a footrest with two chair legs of a chair, said interlocking device having at least - a first locking rod and a second locking rod, and - an adjusting means interacting with the two locking rods (11a; 11b), wherein - said adjusting means being mounted to rotate about an axis of rotation, - the two locking rods (11a; 11b) being disposed coaxially with respect to each other and spaced apart from each other and each being arranged perpendicularly with respect to said axis of rotation, - the two locking rods (11a; 11b) being each coupled to the adjusting means, and - rotation of the adjusting means about the axis of rotation causing the two locking rods (11a; 11b) to synchronously move in opposite directions, said two locking rods (11a; 11b) having each a rod extension (12a; 12b) which is designed so as to extend at least section-wise radially outwardly from the respective locking rod, the sections of the rod extensions (12a; 12b) designed to extend radially outwardly running on two opposite sides of the axis of rotation and the two locking rods (11a; 11b) being coupled to the adjusting means via said rod extensions (12a; 12b), characterised in that - the rod extensions (12a; 12b) have each an elongated hole formed on the radially outwardly extending sections, said elongated hole being essentially parallel to the axis of rotation and the longitudinal axis of the elongated hole being essentially perpendicular to the longitudinal axis of the locking rods (11a; 11b), and - the adjusting means has two pins (14a; 14b) arranged thereon, the first pin engaging with the elongated hole of the first rod extension and the second pin engaging with the elongated hole of the second rod extension, the pins being movable within their respective elongated hole relative to said elongated hole as the adjusting means is turned about the axis of rotation. - a first locking rod and a second locking rod, and - an adjusting means interacting with the two locking rods (11a; 11b), - said adjusting means being mounted to rotate about an axis of rotation, - the two locking rods (11a; 11b) being disposed coaxially with respect to each other and spaced apart from each other and each being arranged perpendicularly with respect to said axis of rotation, - the two locking rods (11a; 11b) being each coupled to the adjusting means, and - rotation of the adjusting means about the axis of rotation causing the two locking rods (11a; 11b) to synchronously move in opposite directions, - the rod extensions (12a; 12b) have each an elongated hole formed on the radially outwardly extending sections, said elongated hole being essentially parallel to the axis of rotation and the longitudinal axis of the elongated hole being essentially perpendicular to the longitudinal axis of the locking rods (11a; 11b), and - the adjusting means has two pins (14a; 14b) arranged thereon, the first pin engaging with the elongated hole of the first rod extension and the second pin engaging with the elongated hole of the second rod extension, the pins being movable within their respective elongated hole relative to said elongated hole as the adjusting means is turned about the axis of rotation.