Rikers display

[Wolf89]

How do I keep shark teeth pressed up to the glass of a Riker case? They all fall all over the place, when I pick it up

[Kosmoceras]

Put some extra cotton wool or foam behind the main padding material. 

[goatinformationist]

But never use glue.

[Troodon]

I've used white felt over the entire field, with small teeth, to keep them from getting tangled in the fibers and added thickness.  I've experimented with different thickness in boxes.   

[ynot]

Segregate them by thickness so very thin are not near very thick.

You can also stuff the backing with paper.

[Past Hunter]

Be careful if you transport your fossils in these with the case full pressing your fossils against the glass. You need to place something between the fossils and the glass. I put my teeth in these and I noticed a spot on the front of the lobe where it made contact with the glass. 

[caldigger]

I usually use bubble wrap (smaller bubbles) under the poly/cotton fill. This adds the needed thickness and some springiness to further cushion the delicate fossils.

It's also cheap since it usually comes with fossils in the mail.