Plan for wings first with a Leghorn
Most heavy laying hens escape at ground level, but a Leghorn adds a second direction: up. Light-bodied, athletic, and easily startled into flight, she can clear a respectable fence from a standing start and do considerably better with the run-up or launch point a coop roof edge, feeder, or perch provides. She is also slim enough to use gaps that a broader hen cannot, and active enough to find them during a day of constant foraging. A proper check therefore starts by looking up at the cover and the launch points, then works down the sides to the small holes and lifted edges at the base, finishing with doors that people use daily and secure least carefully.
Audit the top cover and remove the launch pads
Stand inside the run and look for sky. Any uncovered section, torn netting, or sagging cover with a gap at the edge is an exit for a Leghorn regardless of fence height, so trace the cover to where it meets every wall, tree, and coop side and confirm it is fixed continuously rather than draped and weighted in places. Check fixings after wind, because a cover that lifts at one corner teaches the flock the route within a day. Then map what sits beneath gaps or lower stretches: feeders, water stands, stumps, stacked crates, and the coop roof itself all raise her starting height, so move movable items toward the middle of the run and treat the roof line as fence height when you judge a nearby stretch.
If the run is uncovered by design, be honest about its height from those raised starting points rather than from the ground, and watch whether birds already land on the top rail, since a hen who sits on the rail has solved the problem and is only deciding when to drop down the other side.
Work the sides and base for a slim, busy hen
Walk the outside of the run slowly, pushing wire gently at intervals to find a section that bows outward, a broken tie that leaves a flap, or rusted mesh opening into a hole at body height for a chicken. Crouch for the base, where the common failures are wire that stops short of the ground on a slope, an edge lifted by scratching along the line, and gaps around posts and corners that widen as soil is worked away. Leghorns scratch energetically, so check the corners and the strip under feeders weekly for a developing scrape that is becoming a doorway. Fill and pin the base so there is no inviting dark gap, and repair a hole with overlapped, firmly fixed material rather than a twist of wire she can worry wider.
Doors, pop holes, and the daily-use weak points
Open and shut the run door as you do on a rushed morning, then check whether it still latches fully when pulled to without attention, because a door that needs a lift and a jiggle will eventually be left a finger's width open, which is plenty for this hen. Test the pop door between coop and run in its closed position for a warped edge or worn catch, and look for gaps around feed hoppers, external nest boxes, and any panel you remove for cleaning, all of which sit at chicken height and are handled often. Keep vegetation cut back from the outside of the wire so you can actually see the base during checks, and make a full circuit after storms, repairs, or moving equipment in the run. If a Leghorn still gets airborne and lands two gardens away, her record on KinsLe in the Lost Pet Alert System spreads word around the neighbourhood and helps the householder who catches her contact you for collection.