How to use one Mac as a Time Machine destination for another

“Here’s a strange (but interesting!) thing you can do with APFS under Mojave and High Sierra: You can designate a Mac as a network Time Machine destination, so in a pinch, you could back up one Mac in your house to another,” Melissa Holt writes for The Mac Observer.
“I can see this being useful if, for example, you’re concerned about potentially failing hardware on a machine and want to get it backed up before you can even run to the store to get an external drive,” Holt writes. “In that scenario, this feature could really save your bacon!”
“To configure this, start on the Mac you want to back up to,” Holt writes. “As I noted, this machine will need to be using APFS, so you’ll have to have High Sierra or Mojave installed.”
Easy-to-follow directions and screenshots here.
MacDailyNews Take: You can also use this for MacBooks with limited storage capacity. Have the MacBook(s) back up to your capacious iMac.