Use an IOA shelf (also called an IOA bracket) when installing half-height IOAs in the router. IOA shelves screw into the midplane between the upper bay (Adapter 0) and lower bay (Adapter 1). IOAs in the upper bay rest on the shelf, while IOAs in the lower bay use the guides on the bottom of the shelf to remain vertical. See Figure 13.
Figure 13: IOA Shelf
We recommend that you power down the router before installing an IOA shelf between two slots that have modules installed in them already. Otherwise, you might short-circuit the installed modules if you accidentally touch the shelf to a module.
To install an IOA shelf: