I recently received an email from a weaver named Cindy, in regard to profile drafting and tie-ups. She was curious about the ability to use 8 harnesses with a 4 block profile draft. And furthermore, how do weavers know which harnesses to assign for the tie-up from a profile draft? Her questions were geared towards the particular structure M's and O's, so that is the structure I will be using to explain.

According to The Handweaver's Pattern Directory, by Anne Dixon, M's and O's have two distinct block types: tabby and texture. The texture is a loose weft rib in the cloth. A block (or profile) is drafting short hand intended to help simplify the reading of a draft.

For example:

Block A (straight block) is equivalent to:
1,2,1,2/3,4,3,4

Block B (broken block) is equivalent to:
1,3,1,3/2,4,2,4

Instead of writing the following down for a draft:
1,2,1,2,3,4,3,4,1,2,1,2,3,4,3,4,1,3,1,3,2,4,2,4,1,3,1,3,2,4,2,4

You can simply write:
AABB
SO SIMPLE!

Now, this concept can be expanded so that you can have more blocks to play with. With four harnesses, only two blocks are available to work with; A and B as listed above. With eight harnesses however, you now have FOUR BLOCKS to work with!

Block C = 5,6,5,6/7,8,7,8 (straight block)
Block D = 5,7,5,7/6,8,6,8 (broken block)

In order to see this to fruition in your computer program of choice (mine is Fiberworks/PixeLoom), you should MANUALLY put these in. I have tried using the block substitution tool in Fiberworks and I developed the same results as Cindy: a 10 harness draft. However we want to use 8, so I went in and tested putting in the block substitutions manually, and I was able to achieve the desired effect.

The next part of the question is in regard to understanding which harnesses to apply to the tie-up. What I found to be the best method of looking at it was to break the tie-up portion of the draft into quarters. The original 4 harness structure for M's and O's is our starting point. Block A and Block B have the same tie-up structure:

For the sake of clarity I have repeated each block TWICE in the following drafts

The tie-up for these two blocks equals one quarter of the future tie up in the 8 shaft pattern. Block A is Black and White and Block B is Yellow and Cream to differentiate the two blocks.

The next step is to fill out the rest of your tie-up quarters. I first, tried to figure out through trial and error what would work best for the remaining blocks (Block C and Block D). I copied the exact tie-up presented above into the right hand quarter.

If we take the same tie-up and reverse it into the two remaining quarters the result would be as follows:

When we do this, we basically repeat the SAME blocks just in different positions in the weaving (Blocks A and B in red and Blocks C and D in green). This is not particularly enjoyable- especially since we should have four blocks to work with to create a unique pattern. I started getting frustrated and not able to create anything close to what I was envisioning.

It's at this point that I remember I have an invaluable resource for eight harness weaving: A Weaver's Book of 8-Shaft Patterns from the Friends of Handwoven, edited by Carol Strickler.

"For the 4-block "grouped" M's and O's, the tie-up is attained by stacking two 4-shaft tie-ups in all their different combinations."

From this information we see that there are three different combinations to play with. Again, for the sake of clarity, I have repeated the block threading (pictured is Block A or C) twice AND the tie-up twice in each graphic.

Now that we have this knowledge under our belts we can go back to our big eight shaft draft.

I had gone through and stacked one of each 4-harness tie up within each section of the tie-up grid. With each cross-section you can see either cords, plain weave or a texture. Therefore, allowing the blocks to be woven independently or combined as desired.

In the end, I am saying there are methods to create your blocks on an 8 harness draft, and it depends on how you want your weaving to look. The best way I found is through looking at the pairing of the 4-Harness tie-ups and what structure is going to be created.

I hope that clears some mystery up for those exploring this avenue of drafting and weaving. If you have any further questions, I will do my best to clear up what I presented and answer what I can. Cheers!