Bicycle saddle bags are small, often wedge-shaped bags designed to fit under the seat. The bags hold small items such as spare inner tubes, CO2 cartridge pumps, energy bars or bicycle-tool kits. Many companies produce these bags, but the bags all are attached to the bike in similar fashion.

Position the saddlebag so the wedge angle is facing the seat stem tube. Open any hook-and-loop material fasteners at the front of the wedge, or unclip any plastic quick-clips. Undo the hook-and-loop straps on the top of the saddlebag and place them so they hang off the side of the bag.

Push the saddlebag under the seat and wrap the front wedge straps around the seat stem. Marry any plastic quick-clips together or attach the hook-and-loop material straps together so the bag hugs the seat stem.
 
Thread the upper saddlebag hook-and-loop straps through the seat bars under the seat. Most bicycle seats have one of two metal bars underneath. Thread the two saddlebag straps through these bars and attach the hook-and-loop material together, securing the saddlebag to the underside of the seat.