UKH

I bought some ball nuts on a whim (they were heavily discounted). I haven't had a chance to climb on them yet but I've played around with placing them in a crack.

There doesn't seem to be very much information on using them on the web. Does anyone use them regularly?

I can't find anything about placing them in horizontal cracks. I don't see why this would be any worse than a nut or cam in a horizontal crack. It's not obvious to me, however, which way up they'd go. Ball down I think puts less bending force on the wires, but ball up seems more mechanically secure. Thoughts?

Not used them for a while, but I’ve fallen on them many times in horizontal cracks.  Held every time.

Doesn't answer you question but some good user advice.

https://www.vdiffclimbing.com/ball-nuts/

With horizontal features I've gone for the best fit rather than be concerned about ball up or ball down. Never had one let me down yet.

Another vote for best fit. More likely to get stuck than to fail after weighting if placed well. 

If you're putting your balls in the crack you're doing it wrong! 

I have some on my rack, the red blue and yellow one. Have fallen quite heavily on the yellow before and it held fine, but I had to come back with a hammer and a screwdriver to get it back out. 

Unfortunately the wire to the ball on the yellow one has now deteriorated and when I press down the wire sort of kinks on itself and I haven’t been able to place it lately so I’m thinking it may need retiring. 

As for horizontal cracks I personally would go ball up.