In my WOW study group we have been studying profile drafts. The design chosen by my small group had 6 blocks. With a 12 shaft loom a 6 block rep weave could be produced. The weft has one thick and one thin thread.
Rep is a warp dominate weave. This means the threads per inch in the warp is large. (Double the number in a balanced plain weave for that yarn size.) The weft has one thick thread followed by one thin thread.