The sleeve is made with old carpet, fastened at the trailing edge.
It is attached to a base at about a 25-30 degree angle upward and mounted to a table at convenient working height.
The thrust of the running engine cocks the airplane to the right and makes the TE dig into the sleeve and hold fast.
I recommend pegging the safety thong to the ground in case something goes badly.
So then you run out, pick up the handle and step back.