Is it supposed to be a trailing cactus

It's probably a prostrate form. Many with thin stems have that habit.

Thanks Hywel. Oh dear does that mean it will spread outwards?

unusual shape, but nice

It is looking very healthy but I could do with it staying that size.

I am not a cacti fan but I do like this one,

It will probably hang down over the pot. I don't think it will stick out at right angles lol.

Next time we repot it I could try it in a hanging basket and see if it hangs down.

This is a real fooler. Pretending to say, "touch me". I like this weird sort of thing. Nice color, and it would be nice if it just stayed this way. Soooo glad you showed it. I meant to ask you, what is that wonderful blue it's sitting on?

Thanks Wells I'm glad you like it. The blue is a shaped painted wooden trolley for moving plants around. To stop it from falling off the windowsill I took the castors off. It saves the pine top of the cupboard from spills of water etc. too. It was that colour when I bought it.