To get into this sex position, a penis-owner squats down to present their penis to their partner who sucks the receiving-partner's penis while resting on their knees and elbows.
This sex position gets its name because the performing-partner’s position resembles the position of a plumber getting underneath a sink for repairs.
While the plumber position does not leave a lot of accessibility to include sex toys, it is still possible. For example in the image above, the giving partner is enjoying an anal toy (like the Thump-It, Satisfyer Love Beads, Odile, b-Vibe Snug Plug, or Nexus Simul8) while performing fellatio, which allows for both partners to receive stimulation at the same time. The receiving partner can also use a butt plug during this position, if they want to.