This 23" wood shelf is 23" long and made of 8" wood, so it measures approximtely 23" x 7.5". Good size for a chinchilla to enjoy!
Why a 23" shelf, you ask?  Because 23" is the size that fits in Ferret Nations & Critter Nation cages from front to back.  Perfect size to replace those plastic shelves with wood! 
Bolts can be installed however you want -- long side, short side, one long & one short, and so on...
Please note: the shelf in the picture looks a little rough -- it is simply an example to show you the length (23") of the shelf.  
Which side do you want the bolts on? Short side? Long side? Both? Custom?