What is "rack rail"

Rack \Rack\, n. [Probably fr. D. rek, rekbank, a rack, rekken to stretch; akin to G. reck, reckbank, a rack, recken to stretch, Dan. r[ae]kke, Sw. r["a]cka, Icel. rekja to spread out, Goth. refrakjan to stretch out; cf. L. porrigere, Gr. 'ore`gein. [root]115. Cf. Right, a., Ratch.]

1. An instrument or frame used for stretching, extending, retaining, or displaying, something. Specifically:

   1. An engine of torture, consisting of a large frame, upon which the body was gradually stretched until, sometimes, the joints were dislocated; -- formerly used judicially for extorting confessions from criminals or suspected persons.

      During the troubles of the fifteenth century, a rack was introduced into the Tower, and was occasionally used under the plea of political necessity.
      --Macaulay.

   2. An instrument for bending a bow.

   3. A grate on which bacon is laid.

   4. A frame or device of various construction for holding, and preventing the waste of, hay, grain, etc., supplied to beasts.

   5. A frame on which articles are deposited for keeping or arranged for display; as, a clothes rack; a bottle rack, etc.

   6. (Naut.) A piece or frame of wood, having several sheaves, through which the running rigging passes; -- called also rack block. Also, a frame to hold shot.

   7. (Mining) A frame or table on which ores are separated or washed.

   8. A frame fitted to a wagon for carrying hay, straw, or grain on the stalk, or other bulky loads.

   9. A distaff.

2. (Mech.) A bar with teeth on its face, or edge, to work with those of a wheel, pinion, or worm, which is to drive it or be driven by it.

3. That which is extorted; exaction. [Obs.]
   --Sir E. Sandys.

   Mangle rack. (Mach.) See under Mangle. n.

   Rack block. (Naut.) See def. 1 (f), above.

   Rack lashing, a lashing or binding where the rope is tightened, and held tight by the use of a small stick of wood twisted around.

   Rack rail (Railroads), a toothed rack, laid as a rail, to afford a hold for teeth on the driving wheel of a locomotive for climbing steep gradients, as in ascending a mountain.

   Rack saw, a saw having wide teeth.

   Rack stick, the stick used in a rack lashing.

   To be on the rack, to suffer torture, physical or mental.

   To live at rack and manger, to live on the best at another's expense. [Colloq.]

   To put to the rack, to subject to torture; to torment.

   A fit of the stone puts a king to the rack, and makes him as miserable as it does the meanest subject.
   --Sir W. Temple.

A Rack rail, or rack strip, is used to mount rackable electronic hardware and 19-inch rack mount accessories within a 19-inch rack. Within a rack a minimum of two rack rails are required to mount equipment. The height of rack rail is determined by the number of rack units required for mounting the equipment.

Each rack unit (U) is equivalent to . Most rack rail is in sizes from 2 units high to 45 units high .