Olympian Michele Mueller has had to contend with keyholes at various times in her riding career and says the best way to deal with them is to treat them like any other jump. She says with a little imagination, you can practice over a reasonable facsimile of this obstacle at home.
“The first time I did a keyhole was at the Richland Park Horse Trials in Michigan and my horse just jumped through it without any issue. Some horses feel like they are ducking as they are jumping through one, but it doesn’t take long for them to get over the tendency to duck.
Because keyholes aren’t introduced until the higher levels, by then you should have a confident horse on cross-country that trusts what you ask of it and jumping through a hole should be uneventful. But it’s not something you want to try with a green horse.
You can simulate a keyhole jump at home. I have a chevron between two cedar trees and usually I cut the trees back, but I’m letting them grow in from the sides to create that feeling of a hole. I like cedar, as it’s soft if you or the horse brush against it. Generally, you want to simulate a keyhole with a narrow fence and high sides.
I’ve also seen someone create a frame out of 2×2-inch strapping with a short, stiff material tacked to it that could be used with regular standards. Before the indoor eventing competition at the Royal, Ian Roberts simulated some of those elements we’d have to deal with at the Royal in his arena at Dreamcrest Farm. He even hung burlap netting from the rafters that you jumped through over a portable cross-country jump.
You want to make sure you create enough headroom if you’re simulating a keyhole at home. (According to FEI course design guidelines for hole fences, the height of the hole should not be less than 1.80 metres and the width not less than 1.60 metres. Any surface that can be touched by the horse must always be soft, not likely to hurt the horse or the rider, and the spread should not be more than 50 per cent of that permitted for the level.)
Even at the highest levels of eventing I haven’t encountered many keyholes. Some jumps aren’t really holes, but more like large picture frames you jump through.
As I’ve said, this is not an element you want to try with a green horse or a horse that lacks confidence. If your horse is an experienced event and confident, ride it like you would any other fence. Stay straight, keep your line and ride with intent. Don’t get forward, don’t crunch your body or duck. Don’t look up; look through the jump to where you’re heading. Ride it like a regular jump and you may be surprised at how confidently your horse jumps it.”