If you are getting into rope play, then you really need to consider getting something like this.  A rope cutter. Not necessarily for routine use during the session, but it should be kept somewhere close so that you can get someone out of bondage very quickly.  There might be any number of reasons for this. The sub might unexpectedly panic and need to be released. A knot might not be able to be untied as planned. Someone might start to loose feeling in a limb. A house mate, or worse parent, might come home unexpectedly.  They only cost a few dollars and are available from major hardware stores. In the model below, the yellow cover has been removed. Better safe than sorry!   🙂