Tri-fold Kneeboard (IFR)

The advantage of a tri-fold kneeboard is the additional side pockets that sit on either side of the pilot's knee. The top surface (the middle part in the above illustration) is a normal IFR clipboard which holds charts and worksheets during flight, and is imprinted with useful IFR information such as flight plan filing sequences, etc. Backup documents and charts will fit in the side pockets.

On the other hand, the Jeppesen tri-fold has a particularly handy way of folding up for storage, and comes with a free plotting chart.