The doors on an MKIV tank opened outwards, so that means you had some protection when you where leaving the tank. They also each had a shooting hatch and a periscope at eye level. With a male tank they fired 6-pounder ammunition, which always left the copper casing, which they could discharge through the container at the bottom of the door when it was closed. The hinges of the doors were all made upwards and the Germans knew this, ..., could simply lift the door and throw a grenade in, on the later versions of these tanks the top hinge was turned over to prevent this.
Our doors are still under construction in Dorset (England), using rivets from the old steam engines!
To be continued!