How do you fix a horse that drifts left or right over fences?

A horse that consistently drifts to one side over fences — moving its body laterally through the jumping arc rather than maintaining a straight trajectory — is showing either a physical asymmetry, a training gap in straightness, or a response to a specific fence type or location that causes it to avoid jumping straight. The first step is identifying whether the drifting is consistent in both directions — a horse that always drifts right over fences set in all locations and all types is likely showing a physical preference or asymmetry — or whether it is specific to certain fences or certain locations in the arena, which suggests an environmental or context-specific cause that is easier to address through specific training. Physical causes including asymmetric leg strength, back soreness that causes the horse to drift away from the painful side, or vision problems in one eye can produce consistent drifting that training corrections alone will not resolve, making veterinary assessment appropriate when drifting is severe or persistent. For training-based drifting, placing a ground pole parallel to the fence on the landing side in the direction of the drift — a guide rail that physically prevents the horse from drifting in that direction — can develop the habit of landing straight before the training correction of the drift is addressed through aids alone. Riding on a straight track between two guide rails or poles set at fence width on either side of the fence develops straightness through the fence by limiting the available space for drifting. The rider's aids also contribute to or correct drifting: a leg that is too strong on one side can push the horse to drift away from it, while a consistent opening rein on the drift side can correct the trajectory without the pulling on the outside rein that typically makes drifting worse. Ground poles placed as wings extending from the fence standards on both sides can also help guide the horse through a straight trajectory.