title_body: How does one hold the motor bell still when tightening prop nuts? Almost all of the brushless motors used in hobby-grade multirotors have a single threaded shaft and rely only on friction between the propeller and motor to keep the prop from slipping. This means that the nuts holding the propeller down must be tightened with considerable force. 
  
  When I try to do this, however, while I have a good grip on the nut (via a wrench), I can't hold on to the motor itself very well to keep it from spinning together with the nut, and if I try to hold on to the propeller, it cuts me with its sharp edges. What are the available tools and/or techniques that can aid in keeping the motor still while tightening or undoing the prop nut?
upvoted_answer: You know those rubber wristbands that are given out at lots of events?
  
  You can wrap one of those around the motor bell to get better purchase on it, and then torque down the prop nut.
  
  There are also specialised tools to hold motor bells, such as the one pictured below which can be found here, on Thingiverse.