You then need to nail the tunnel to the entrance hole, by nailing it from the inside of the crate, so make sure the main entrance hole is smaller than the tunnel’s dimensions.
If your box doesn’t have pre-existing holes, drill a few small holes down the sides for ventilation. An alternative is to drill a large hole at the back and place a piece of old hose pipe through it to get air in there for the hedgehog.
Place the box in a quiet part of the garden, underneath a hedge. Hedgehogs like to make themselves at home so don’t put anything inside the box, and instead place dry leaves, grass and straw all around it.
If you’re using a crate that has gaps on the roof, make sure you cover it to ensure it’s fairly watertight.
Hedgehogs tend to move hibernation areas once or twice during the winter so make sure you don’t get rid of any house you put outside if you can’t see anything in there, leave it out for the next resident!