How to make a low balcony railing safer?

[ExpectTheWorst]

Low as in both the balcony is low (cats could I think quite easy jump down off it without hurting themselves), and the railing itself is low enough for them to jump directly up onto it (but not wide enough to sit on). There is no roof.
I don't think we need netting, but I'd like to discourage them from jumping down/over AND give them a safe ledge to sit/sleep on (but not roll off).
Has anyone done anything like this? I'm thinking a wooden ledge all the way round and then some sort of small guard or something - I've seen people do this with plexiglass to stop cats rolling off open stair ledges. Any ideas welcome!

If the balcony is quite low, is it that you want to keep them in? Just trying to make sure I’ve understood.

The plexiglass might work to give them a more comfy sleeping ledge but unless you make it pretty high I could see them jumping over the top.

Could you post a picture, how much iff the ground is the balcony ?

I was thinking plexi glass as well

Sorry just seen there’s replies to this!

Yes, I’d like to stop (or very much discourage) them jumping down and wandering off (we may well install a cat flap downstairs at some point but I still want to know if they’re at home or not).
I’ll try and draw a diagram.

Unless you box it in if they want to go they will go. My neighbours thought similar of their three storey house top floor windows leaving them open. Their cat just leapt out, she landed on her feet and was fine.

Yes, I realise that, but the way it is atm the railing is not at all wide enough to sit/lie on, so if they jump up there there is a good chance they will fall or slip off the other side, so I'd like to make it safer for them - if they're sitting safely up there then I guess then can decide themselves if they want to try and jump down, but I don't want them accidentally falling off.