Each process in the setup of the loom is a chance to check the accuracy of the previous process. During threading, I double-check that I wound the right number of threads in each section. During sleying, I check my threading by counting through my pattern as I count out the threads into their dents. With each thread, I have two numbers in my head, the harness number and the number of threads in the dent.
For example, the threading for one section is:
6,7,8,1,2,3,4,5,6,7,8,1,2,3,4,5,6,7,8,1,2,3,4,5,6,7,8,1,2,3,4,5,6,7,8,1,2,3,4. That's 39 threads.
The sleying for a 15-dent reed is 1-1-2-1-1-2-1-1-1-2, repeated 3 times. 13x3=39.
So, to check the threading while sleying I count like this:
1,6 - 1,7 - 2,8-1 - 1,2 - 1,3 - 2,4-5 - 1,6 - 1,7 - 1,8 - 2,1-2
This takes some getting used to, but really cuts down on the time I spend fixing threading errors while I'm weaving the sample blanket.
After a section is sleyed, there's one last check - that the section really measures 2" in the reed.
See the empty third dent? This is a really easy mistake to catch. Usually it's a matter of too many 1's or two many 2's leading to the count being off.
I would much rather catch a sleying mistake now and resley one section than to get to the end of the reed and have too many threads or too many dents.
See? It's easy to tell that the section is right by just keeping the ruler on the track and checking every section as soon as it's done.