slipboard

noun4

1. •
   A board sliding in grooves.

   • I ventured to draw back the slipboard on the roof, contrived on purpose to let in air. — 1726
2. •
   A type of fence consisting of panels or boards held between uprights that have grooves on either side to hold the edges of the two adjacent boards.

   • Slipboard fence as low as $8.67 per 10 foot section. — 1991
3. •
   (UK, historical) A sign that slides into a frame on the front of a bus for displaying special messages.

   • Bristol LD6G 1432, en route to Lymington, carries a slipboard on its radiator stating 'Not on service for Bournemouth Corporation passengers'. — 2019
4. •
   A list of substitute workers that are available in a union-controlled business, listed in priority order and by the shift they would like to work.

   • The parties agree that, on March 14, 1975, the slipboard was frozen. Extras and substitutes shall continue to be hired from the slipboard when needed in accordance with the provisions of this section. — 1978