Tying On to the Cloth Apron
I prefer to tie one warp onto the cloth apron rod at a time. That way I can be sure each warp¹s threads are tied on with even tension. Remember, don’t agonize! To tie on, lift the warp on the upper broom handle by raising the shafts in which it is threaded and hold the shed open. Tug on the warps in the reed for some tension, then the two warps should separate easily. Select the threads from the lower warp and tie on as usual, leaving spaces between the bundles for the second warp to be tied. Check the warp tension as usual. When the second warp is weighted and not on a second beam, tie it in the spaces. (That warp is tensioned when the weights are attached. Be sure to tie on before adding the weights or the threads will pull out of the heddles!)
If you are using two beams, lift the first warp up out of the way to tension the second.
Taken from Book 2, Warping Your Loom and Tying On New Warps