Answers.Body: <p>If I'm understanding you correctly, you're talking about the molding cavity directly underneath the stud (that actually goes up into the stud), and not the main tube cavities under plates/bricks (that are actually offset from the studs).</p>
  
  <p>If that's the case, no, I'm not aware of any element that "intentionally" fits that space.</p>
  
  <p>First off, I don't think that space is made with a high tolerance.  Looking at some of my bricks, the dimensions of that cavity are not nearly as uniform as the other features of the brick.</p>
  
  <p>Secondly, I don't know how many System bricks have components that are not integer multiples of LUs.</p>
  
  <p>You might get lucky and get a minifigure piece that has a detail that is 1.5 LUs, but you'd have to try a lot of them.</p>
  
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Answers.Text: Your interpretation is correct :). Hmm, the part about the tolerance is interesting. I was hoping to fit a "Hand Pirate Hook" in the cavity, sounds like there's still some hope.
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Answers.UserDisplayName: Nick2253
Answers.Body: <p>Without further specification, unless I read your question wrong, ANY normal brick-type element can be connected to the cavity under a stud - the whole principle that LEGO was based on, basically. Anything that has a stud on it will fit.</p>
  
  <p>If you rather meant "non-stud" elements such as hands, signs, rods, etc., please update the question to make it more specific. </p>
  
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Answers.Text: Updated the question.
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Answers.UserDisplayName: Phil B.
Answers.Body: <p>For base plates you can connect the light sabre pieces underneath the base plate but I don't think it was an intentional feature</p>
  
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Answers.UserDisplayName: vorchin
Answers.Body: <p><em>(Edit: after re-reading your question I realized I misinterpreted the stud with the bar. Leaving the answer for posterity.)</em></p>
  
  <p>There is. The size in the small holes beneath newer plates is the same size as a connector that doesn't have a fixed name. Bricklink calls it pin, others call it mini pin or stub. It is used in minifig headgears and a few other places, like the old dragon flame. It's not a connection people often use, but it can be done:</p>
  
  <p><img src="https://i.sstatic.net/TyK6Q.jpg" alt="Using the mini pin"></p>
  
  <p>This picture is taken from <a href="http://www.dagsbricks.com/2013/04/lego-tips-and-techniques-mini-pin.html" rel="nofollow noreferrer">a small writeup</a> by Brian D'Agostine which documents other uses of it. You can also use the same pin (stub, mini pin, teensy tiny peg) to <a href="http://www.classic-castle.com/howto/articles/firestrands.html" rel="nofollow noreferrer">create fire strands</a>:</p>
  
  <p><img src="https://i.sstatic.net/4Mo7i.jpg" alt="enter image description here"></p>
  
  <p>Once you're aware of the connection you can find many fun fits for it.</p>
  
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Body: <p>Are there any elements that can be connected to the 'cavity' (i.e. the space) under a stud (e.g. on a regular plate or a regular brick)? The cavity measures about 2.4mm in diameter. </p>
  
  <p>So far I've only tried a minifig hand peg (not the clip side, the other side) but unfortunately it is just a bit smaller, it has a diameter of about 2.3mm.</p>
  
  <p><strong>[Edit]</strong> I'm talking about the cylindrical cavity with a diameter of 1.5 LU as indicated in the overview posted here -- <a href="https://bricks.stackexchange.com/questions/288/what-are-the-dimensions-of-a-lego-brick">What are the dimensions of a LEGO brick?</a>.</p>
  
Tags: <compatibility>
Title: Any elements that can be connected to the cavity under a stud?
UserDisplayName: Ailurus
ThreadText: # Any elements that can be connected to the cavity under a stud?
  
  (Asked by: username_0 on 2015-02-01)
  
  Are there any elements that can be connected to the 'cavity' (i.e. the space) under a stud (e.g. on a regular plate or a regular brick)? The cavity measures about 2.4mm in diameter.
  
  So far I've only tried a minifig hand peg (not the clip side, the other side) but unfortunately it is just a bit smaller, it has a diameter of about 2.3mm.
  
  **[Edit]** I'm talking about the cylindrical cavity with a diameter of 1.5 LU as indicated in the overview posted here -- [What are the dimensions of a LEGO brick?](https://bricks.stackexchange.com/questions/288/what-are-the-dimensions-of-a-lego-brick).
  
  **Tags:** compatibility
  
  ---
  
  ## 4 answers
  
  ### Answer by username_1 on 2015-02-04. Score: 3
  
  If I'm understanding you correctly, you're talking about the molding cavity directly underneath the stud (that actually goes up into the stud), and not the main tube cavities under plates/bricks (that are actually offset from the studs).
  
  If that's the case, no, I'm not aware of any element that "intentionally" fits that space.
  
  First off, I don't think that space is made with a high tolerance. Looking at some of my bricks, the dimensions of that cavity are not nearly as uniform as the other features of the brick.
  
  Secondly, I don't know how many System bricks have components that are not integer multiples of LUs.
  
  You might get lucky and get a minifigure piece that has a detail that is 1.5 LUs, but you'd have to try a lot of them.
  
  > **Comments:**
  > **username_0**: Your interpretation is correct :). Hmm, the part about the tolerance is interesting. I was hoping to fit a "Hand Pirate Hook" in the cavity, sounds like there's still some hope.  
  
  ---
  
  ### Answer by username_2 on 2015-02-01. Score: 1
  
  Without further specification, unless I read your question wrong, ANY normal brick-type element can be connected to the cavity under a stud - the whole principle that LEGO was based on, basically. Anything that has a stud on it will fit.
  
  If you rather meant "non-stud" elements such as hands, signs, rods, etc., please update the question to make it more specific.
  
  > **Comments:**
  > **username_0**: Updated the question.  
  
  ---
  
  ### Answer by username_3 on 2015-02-14. Score: 0
  
  For base plates you can connect the light sabre pieces underneath the base plate but I don't think it was an intentional feature
  
  
  ---
  
  ### Answer by username_4 on 2015-02-16. Score: 0
  
  *(Edit: after re-reading your question I realized I misinterpreted the stud with the bar. Leaving the answer for posterity.)*
  
  There is. The size in the small holes beneath newer plates is the same size as a connector that doesn't have a fixed name. Bricklink calls it pin, others call it mini pin or stub. It is used in minifig headgears and a few other places, like the old dragon flame. It's not a connection people often use, but it can be done:
  
  ![Using the mini pin](https://i.sstatic.net/TyK6Q.jpg)
  
  This picture is taken from [a small writeup](http://www.dagsbricks.com/2013/04/lego-tips-and-techniques-mini-pin.html) by Brian D'Agostine which documents other uses of it. You can also use the same pin (stub, mini pin, teensy tiny peg) to [create fire strands](http://www.classic-castle.com/howto/articles/firestrands.html):
  
  ![enter image description here](https://i.sstatic.net/4Mo7i.jpg)
  
  Once you're aware of the connection you can find many fun fits for it.
  
  
  ---
  
  