A close pipe nipple is designed so that when it is installed there is very little or no gap between the two fittings which attach to either end.
What is the proper method to install one of these? Could be black iron, brass, etc.
Here are the issues I wonder about:
When attaching the nipple to the first fitting, it seems you would have to grip the nipple by the threads with a pipe wrench. This may cause damage. Perhaps a protective padding is used?
When attaching the second fitting, how to ensure the nipple is inserted more or less evenly? The insertion torque may continue to tighten it into the first fitting which would be hard to prevent or even observe.
Should you just tighten both fittings simultaneously?
Example of a close nipple: