What are Butt-Welded Pipe Fittings?

2 sections of pipe with no threads but just smooth ends are brought together and these are welded in a complete circle to seal it off . making it water-tight.  Copper water fittings are not butt welded.  they usually have a sleeve (called a coupling) that each section of pipe fits into these are 'cleaned' usually with sandpaper or emory cloth.  Then 'flux' is applied, and finally solder is applied .. it is heated and melts, seeping into the joint sealing both sections and making it water tight.  Plastic pipes are not butt welded either.  They also have couplings that the 2 'joints' or sections of pipe are slid into. They are also cleaned to get rid or litte bits of plastic,  then they are glued together in the sleeve by a glue which starts a cem reaction to melt the outer layer of plastic so that they fuse together and make a water tight seal.

This is not a question about Chemistry.  It needs moving.

it's a method of welding 2 plastic pipes together

https://www.youtube.com/watch?v=-SEVTKO8g4Y

Sounds like it could be painful. Why is it posted in chemistry?

End to end. Butted together.