Just replacing the kitchen gas hob for a new one. It comes with a
right-angled pipe (an elbow), one end of which goes into the hob and one end
into the copper supply pipe.

The *threaded* part of one end of the right-angled pipe is about 4mm longer
than the threaded part of the other end.

Would it be the *longer* threaded part that goes into the hob or the
*shorter* threaded part?

Since I was supplied with a rubber washer to go into the hob connection
joint, should I use gas tape on both the threaded ends of the right-angle
pipe. Thanks for advice.