I lunge and jump my horse with bell boots. It's to protect the front hoof from overreaching, but when I lunge and jump the chance increases. When she first started jumping, she'd hit the pole with her hoof, so that's why I got them. Now if she does, she'll hit the bell boot.
I also put her bell and splint boots on when I let her run like the wind in an arena. She just gets so happy to run that i'm afraid she'll nic herself.
That all I use bell boots for