Primary backing fabric
Primary backing fabric is the industry standard material for rug tufting. It is a professional quality material that will create durable, high-quality rugs. The material is highly suited to detailed work because it is forgiving on diagonal and curved lines.However, primary backing fabric is not as commonly available in fabric stores when compared to other materials. If you are on the hunt for this material, you will likely be able to find it online but you may have to commit to buying a large quantity.
Monks cloth is a loose even-weave cotton fabric that is commonly used for punch needling. Monks cloth is heavier and less flexible than primary backing fabric. It is commonly used by rug tufters and is often available in local fabric stores too.
Some users have issues with monks cloth where they find it loosens up from the frame during the tufting process. This can make it difficult to use monks cloth in the rug tufting process. The material can also fray and leave small fibres in the finished tufted rug.
Burlap
Burlap has a very open weave and is available at many fabric stores. It is the most affordable option of the three materials. The quality however differs per product and comes in many different weights. Burlap could work, but some variants tend to tear more easily than other. It may be a bit tough to see your sketches through the burlap material due to how open the weave in the material is so keep this in mind if you choose to use this material.
References:
https://www.youtube.com/watch?v=h-AfpO683o8&ab_channel=SamMadeThat
