Tony M Jul 19, 2019:

@ Asker: Context? The use of the term 'convert' here is curious, and doesn't seem to me to correspond to any of the suggestions received so far. I think the only way to resolve this will be for you to study carefully the relevant figures and try to relate them to the part numbers given.
To me, using 'convert' in EN implies almost that the front wall 'turns into' or 'becomes' the back wall, with no suggestion of any kind of 'join'.