The frame for the Saxon geteld
The only parts of the tent frame which can be seen in the manuscript illustrations are the ends of the ridge pole where they emerge from the sleeve at the top of the tent. It seems reasonable to assume that the ridge was supported by two uprights inside the tent in the same manner as modern "traditional" ridge tents.
The poles can be of any wood that would have been available, although stronger wood will allow you to use lighter poles. Ash would appear to be a good choice: it was used for spear shafts because it is straight grained and very strong. Ash is however relatively expensive and not always available. For our tents we used materials that were to hand, or easily available. The uprights for the small tent are roughly 3½cm circular cross section (wood unknown), and the ridge is about 4½cm round section with one side flattened (a piece of round banister rail).
Cutting and fitting the tent poles is a job best done with the help of a friend and the tent canvas. A very large tent will require a group outing to a very big field!
Insert the ridge pole into the ridge pole casing, mark the position where it will be attached to the two uprights, take it out again, and make the joints.
For maximum authenticity use a loose fitting mortise and tenon joint. As the joints do not show when the tent is assembled you can get away with a steel pin. If using a steel pin you should ensure that the pin is a tight fit in the upright, and a slightly loose fit in the ridge pole. Remember that wood expands when wet. You should make sure that the poles will not lock together in bad weather.
Put the tent and poles together and adjust their length until it looks about right. It's difficult to be precise about this point, but it's better to err on the long side until you have checked. If the tent when put up looks a bit too tall, you can always trim a bit more off the uprights, but it's difficult to put more length on if it's too short!