What is the proper term for the "female" section of the piece that the "studs" insert into? I have heard "pipes", "tubes", "underbits". Is there an actual term for the female section?

  • 1
    Interesting question. To help finding a good term, it would be useful with a good example to use this in a phrase. Do you have an example of use in a natural context?
    – awe
    Jun 5, 2012 at 9:42
  • It was an analogy to demonstrate how you can plug an API into your website. So, the statement went something like "You have a LEGO piece (representing the API) with it's studs and you need to attach it to your website, so you need do build the [underbits/tubes/stud receptacle] to plug the API into."
    – BillyNair
    Jun 12, 2012 at 2:20
  • See also this question for naming other features of a brick: bricks.stackexchange.com/questions/1636/…
    – Jakob
    Nov 6, 2012 at 8:13

3 Answers 3


Chapter 1, Page 4, The Unofficial LEGO Builder's Guide:

The tube is the other half of the mechanism that helps bricks stick together. Tubes capture the studs so that you can join LEGO elements and know they won't fall apart.

  • 2
    I have to disagree on that somewhat, or at least try to add some undertone. The tubes do indeed capture the studs, but not by themselves: the studs are (usually) captured between tubes, or between tubes and brick walls; they don't "insert into" them in conventional builds. Also, not all parts feature tubes, so what would you call the underside of a 1x1 brick?
    – Joubarc
    May 9, 2012 at 7:46
  • The underside of a 1x1 brick? How about "The square version of the tube that is the bottom of a 1x1 round brick"?
    – gev
    Sep 23, 2015 at 16:17

Bricklink (at the time of writing) has 5 catalog items using the term 'stud receptacle'.


Members of the French club FreeLUG refers to these as antistuds, and there is at least one LDraw part that uses that same naming. Considering a lot of other parts don't, however, it's probably not widely accepted. And it's not valid at Scrabble either.

You could also use mortise by analogy with the woodworking assembly (a stud is also usually called tenon in French), but again, I've never heard it in LEGO circles. Slot might be appropriate too.

  • I think "slot" would be more descriptive of an open spot in a construction where a particular part fits.
    – awe
    Jun 5, 2012 at 9:38

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