Abstract: An adjustable platform support mechanism for a keyboard includes a platform and a connecting assembly for the platform. The connecting assembly is attached to the platform by means of first and second pivotal connecting arms. The quadrilateral formed by connecting the pivots is in all instances a non-parallelogram. Thereby the platform, when moved from an extended position to a storage position, is pivoted upwardly in order to increase the space available in the kneehole underneath the desk. The shelf also features an adjustable tilt mechanism associated with keyboard platform support bracket so that the operator will be able to adjust the platform to any one of a number of tilt positions.