Gateways: wide, straight and fully open
A standard gate that a young horse threads without thinking becomes a negotiation for an old one who cannot step sideways or back up quickly. Widen his regular gateways where you can, hang gates so they swing right back flat against the fence, and make a household rule that he is never asked to squeeze past a half-open gate. If he must pass a bottleneck daily — a yard entrance, a stable doorway — clear everything from it: no parked barrows, no protruding bolts, no step up he has to haul stiff forelegs over.
Ground where he cannot afford a slip
More old horses are hurt at gates than anywhere else in the field, because that is where mud, crowding and turning meet. Scrape and drain the gateway patch, lay hardcore or mats where it churns, and route his daily path away from slopes he must cross when wet. On icy or greasy ground, lead him the long way round if the long way is level — a senior who goes down awkwardly may not get up unhurt, however calm he is about being handled.
Fencing his eyes and body can respect
Fading eyesight means plain wire and single-strand electric lines disappear against a background. Use wide, pale electric tape or clearly visible rails on the fences he lives inside, keep strands taut and at heights he will meet with his chest rather than his face, and flag a newly changed fence line until he has learned it. Barbed wire has no place around a horse who moves slowly and turns wide — he is the horse most likely to drift into it and least able to leap away from it.
Teach him the new route yourself
An old horse copes with a changed gateway by learning it, and he learns it from you, not from being driven through it by the herd. The first few times, lead him through the widened gate or the new path yourself, at his pace, stopping where he wants to look; never turn him inside the gateway itself, where his body must pivot in the muddiest, tightest spot — walk him well clear before you turn. After a few calm repetitions the route becomes his habit, and other handlers only have to keep the rules he already understands.
Layout: no traps, no tight turns, no rushing
Walk his field as he experiences it. Dead-end corners, narrow runs between a shelter and a fence, and arrangements that force a hairpin turn to reach water all put him where a livelier companion can crowd him against a barrier he cannot dodge. Give him a loop rather than a corridor wherever possible, place hay, water and shelter so he can leave each from more than one direction, and if the herd plays roughly at bring-in time, fetch him first or last rather than in the middle of the scrum. Then make sure the knowledge is not only in your head: KinsLe Family Sharing lets his profile and handling notes reach every family member and helper, so each person who opens his gate knows his route, his pace and what he needs.