Make a rect in the shape of a wall and make a trigger like this:
Events: Unit enters 'Rect' Conditions: Owner of entering unit = Neutral Hostile (Player Comparison) Actions: Move unit instantly to (Point with Offset) Position of entering unit offset by ..., ... (x, y)
If they come from above: 0, 75 If they come from beneath: 0, -75 If they come from the right: 75, 0 If they come from the left: -75, 0