Additional tracks for added armor were generally tack welded to the hulls and turret sides. Some areas, they were secured by rope or wire to allow access for maintenance etc. On Shermans it was a good thing, due to the extremely thin armor and type ammo used against the tanks. Tracks on Sherman bow plates were often just laid there and didn't have much room to slide around. Nowadays it is a very bad choice to mount anything on the armor, particluarly sloped armor plate. Anything projecting that would impair the enemy round from glancing off would also assist it in penetration.