...for wallpapering!
Re-decorating and DH rolled his ankle while getting off the stepladder an hour in, teen DS1 offered to step in and try his hand. He's a natural! Seams all line up perfectly, bubbles all smoothed out without any fuss, edges neatly trimmed...we'll definitely remember this talent when the time comes to do another room 
Anyone else's DC have a strange knack for things that seems to have come from nowhere? Before today DS's only involvement with wallpapering had been wiping down the paste table when he was much younger!