This reminds us of a story my husband tells. Thirty years ago he designed, manufactured and was trying to market the "Red Wing Viewer" --a traditional wood, leather, brass and glass stereoscope. To pose it nicely for the photographs, Craig cobbled together a little stand to set it on.
Yep: he got inquiries about the stand :-))
So here's all about the easel Craig made for me:
For scale, the easel is supporting a 24 x 36 inch canvass, the easel itself is 20 inches high by 24 inches wide. It could support a 48 inch wide canvass by extending those two metal rods (5/16" rod stock) which are locked by the two 1/4-20 thumb screws on top --which thread into 1/4-20 "T-nuts" (that you can't see). By turning the eccentric wheels, warpage in the canvass' frame can be accommodated (for solid, non-bouncy support).
Even when the table top (a picnic table, say) is very uneven, you simply give the easel a little tug and its two legs equalize their rubber footed grip, giving you firm 4-footed contact.
Thank you for looking at my easel!
Peggy ("Granny" D