The Wooden Horse (1950)

In a POW camp, the Nazis have placed the huts far from the boundary so that any escape tunnel would have to be a long one. One British officer has the idea of starting a daily gynmastics routine using a vaulting horse: they can place it near the boundary and start a tunnel from under it. He and two others do escape the camp by this means and plan to make for neutral Sweden. To do that, they'll not only have to move around without arousing any suspicions, but also find a stranger from a neutral or occupied country who'll be willing and able to help them.