AYC: Because it is possible (bava basara 118b).
- Question
This week’s parsha teaches the issur of shaatnez (the second time). It is known that techeiles may be put in a linen begged because of asei docheh lo saaseh (though we don’t do it today because we treat our techeles as safek), in fact the gemara uses this as a raayah to the din of aseh docheh lo saaseh. I ask, how is it a raayah to aseh docheh lo saaseh if the tcheles thread is only shaatnez d’rabannan?
The answer usually given is that the double knot renders it ???? ???? ??? because it’s fixed there permanently. I claim the question still remains because the tying methods of Rabbeinu Amram Gaon and the RaMBaM (the two with the longest mesorah, the RaMBaM’s being a variation on RAG’s) do not have knots and can be pulled out easily.