As stated, I would very much like to see internal mine doors implemented. I see this as beneficial for several reasons, firstly being the ability to limit access to specific areas of your mine, to others. If you have an ultimate vein of 'something', I doubt you'd be pleased to see your noob cutting their mining teeth on it, so being able to limit access to these resources could be handy. It would also give us the ability to 'lock off' any special areas (ie use of those transmutation rod things) so it's not open to all and sundry. Also, if you have a mine on either side of a canal/tunnel, having a door to and from the canal/tunnel may be helpful. Perhaps they could decay with normal ticks so they wouldn't be up forever and a day, and like reinforcing walls, be able to be taken down by deed owner. Off deed, decay only until they're gone, unlike reinforcing walls which stay around forever. Thoughts?