Measure the gap before choosing the fence
A hedgehog highway works only if the opening is large enough for an adult hedgehog to pass without squeezing. The practical minimum is 13 cm square, roughly the size of a CD case. The wildzy hedgehog-highway method treats that measurement as a fixed constraint, not a rough guide: if the gap is smaller, the route becomes a dead end and the animal will keep using a road or a driveway instead. On a standard 1.8 m close-board fence, cut the opening between posts, not at a post, so the edges stay rigid.
Find the route the hedgehogs already use
Hedgehogs can cover 1–2 km in a night, but they repeat familiar lines along walls, hedges and shed bases. Before cutting, look for flattened grass, droppings, or a gap under a gate that has been worn smooth. A highway placed in a tidy, exposed part of the garden is less likely to be used than one aligned with an existing dark edge. Mark the spot with a cane for a week and check for movement at dusk; this costs nothing and prevents a misplaced cut.
Cut and finish the opening so it stays open
Use a 13 cm square template, drill the corners, and cut with a pad saw or jigsaw. Line the cut edges with untreated timber if the fence panel is thin, because a raw cut in composite board can swell after rain. Keep the bottom of the gap level with the soil, not raised above it; a 2 cm lip is enough to make hedgehogs hesitate. The finished opening should be clear of ivy, stones and long grass, and it should not be blocked by a water butt or bin store.
Manage the strip around the gap, not just the hole
The opening is only one part of the habitat. A 1 m wide strip of leaf litter, native hedging and a small log pile on each side gives hedgehogs cover while they move. Avoid slug pellets within that strip: metaldehyde and ferric phosphate products can harm hedgehogs indirectly by removing their food supply, and dogs or wildlife can encounter the pellets. A shallow dish of water at ground level is useful in dry spells, but it should be no deeper than 2 cm so a hedgehog can climb out.
Check for use without handling the animal
Look for new droppings, disturbed leaves, or a clean trail through the gap rather than lifting the hedgehog. A cheap night camera placed 1–2 m away will confirm whether the route is working; keep it low and pointed at the opening, not at a feeding station. If there is no sign after two weeks, check alignment, clearance and scent barriers such as fresh paint or strong disinfectant. The wildzy principle is simple: build the smallest correct gap, then leave the surrounding mess alone.