Sherman Tank, Hatches- Can they be locked from the inside?

[old tanker]

On US tanks of my acquaintance, all the hatches could be secured from the inside. When parking the tank, all the hatches were secured from the inside with the exception of the loader's hatch which was secured with a padlock. It was possible on a tank so secured to gain access by tapping on the drivers IR periscope mount cover. With a bit of patience and luck you could get the periscope lid to unlatch, then you could reach in a just manage to unlock the driver's hatch. In practice, if the crew has locked the hatches from the inside and the dude outside can just rip it open like in the movies, he does not need the grenade. He should be wearing blue tights with a big red "S" on his chest.