At the front of the hull of the Tiger 1, there were two holes drilled through the armour just above the sprocket wheels. At first they were just plain holes, but early in the production run a steel collar was added on top to extend the hole.
This photograph of the ruined Tiger at Vimoutiers is provided by André Kooijman. Notice that the hole is vertical though the armour is slanted.
Akira Takiguchi kindly provides us with this photograph from a German manual. It shows what is probably the intended use of the hole. It holds a crude jib that hoists the sprocket wheel during a wheel change.
The manual has a sketch that explains how to make a jib.
Another manual suggests camouflaging the tank as a truck, by putting a canvas on poles mounted in these holes. I've never seen a photograph of the holes being used for this purpose.
This is a drawing of the hole and collar, with measurements taken from the Bovington vehicle.
[1] Manual D656/30a, courtesy of Akira Takiguchi