How to keep the blankets from sliding off our RV bed?

If you need rails, why not try the adjustable rods used in bathroom tubs or even the adjustable curtain rods depending on what strength you require.

You might try the peal and stick, industrial strength Velcro. be sure and put ruff loops on bedframe and soft on blanket so when you are sleeping it doesn't ruff you up! This Velcro is incredibly strong and yet easily removable.

Have you tried sheet straps? THey are usually adjustable and clip on to the sheets and wrap under the mattress.

Velcro will be a good idea

Look where medical supplies are sold, or make your own. Have you tried using the clips you can get at most stores that you clip to sheets or whatever and run under the mattress to the other side? Hubby used to use them on his semi since so many mattresses are really thin and the fitted sheets never stayed under the mattress. He swore by them until he got a regular mattress for his truck and then they stayed on finally.

Have you tried using spring rods that are strategically placed? Or how about using PVC pipe...

They make rails like this. I've seen them at bed bath and beyond. They strap under the mattress.

Would something like an adjustable safety rail work? https://www.walmart.com/ip/Bed-Guard-Rail/46343025?wmlspartner=wlpa&selectedSellerId=1656&adid=22222222227033752018&wl0=&wl1=g&wl2=c&wl3=54455697698&wl4=pla-85737787778&wl5=9025395&wl6=&wl7=&wl8=&wl9=pla&wl10=112550034&wl11=online&wl12=46343025&wl13=&veh=sem

https://www.hunker.com/13413380/how-to-keep-blankets-from-sliding-off-the-bed

Maybe wooden dowels would work too.

Tuck in the corners

Can you sew a pocket into the corners that the mattress corners can fit into? Like the shape of a fitted sheet corner.

There’s a company that makes zip up bedding

beddysbeds on Instagram

elderly or infirmed -Try a Mobillity Shop for the

How about a weighted blanket?