extension arm 164 that is shaped like a channel having a top and two sides and an interior cavity two ball bearing glides 168 are secured to the interior walls of the channel and have mounting flanges 166 that extend towards the interior cavity 166 the mounting flanges 166 have holes 170 that allow the extension arm 164 to be attached to plate having corresponding holes similar to plate 155 shown in fig2 but with corresponding attachment holes not shown fig2 shows an alternate embodiment having an extension arm 157 as shown in fig2 with a rotating hinge assembly 171 attached to it the hinge assembly is a known device used for stowing a desktop to the side of a chair used in classrooms and auditoriums the mechanics will be briefly described here a block 172 is mounted to the arm 157 by bolt 176 that extends through a hole 182 located in the center of the block and nut 180 is threaded onto the bolt the block 172 rotates about the bolt 176 the block 172 has two hinge pins 178 located at each end of the block which allows a hinge bracket 174 to be mounted and swivel perpendicular to the axis on which the block 172 swivels the stowable work surface 12 is attached to the hinge bracket thereby allowing the stowable work surface 12 to be flipped up and rotated 180 degrees down and slid back via the extension.