Tri-fold Kneeboard (short)

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 clipboard which holds charts and worksheets during flight. Backup documents and charts will fit in the side pockets. This model (the short version) is recommended for use in small or cramped cockpits. It is also suitable for for short pilots. This model doesn't hold folded aeronautical charts in the side pockets (the pockets are too short). Use the long version if this is an important consideration.

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.