I went to the hangar yesterday and took this photo of the business end of the Aircraft Spruce 87-5 Cleveland brake bleeder fitting:

 

 

This is the end that attaches to the brake bleeder.  The "T slot" on the end slides over the small diameter of the brake bleeder and the shape of the bleeder prevents it from pulling straight out.  The piece you can see inside the 87-5 fitting mates to the end of the brake bleeder when the body of the 87-5 fitting is turned with a hex wrench, providing a surprisingly (at least to me) good seal.

 

Thanks to everyone who contributed to this discussion. 

 

Dennis Johnson

Legacy, with firm brake pedals and a clean hangar floor