My American friend gave my daughter a self-assembly toy and I want to ask her how to assemble it. I found the words rut, groove, ridge, channel and hollow. I want to describe the cuts or dents in some parts that are used to attach something to it. Is "dent" okay? I feel like this word is used for damages. I also saw pictures of 'grooves' on a vinyl record so I'm not sure if it is the proper word. Can you please also tell me in what situations I can use the other words? Thank you.

Please see the picture below. What do you call the hollow one and the protruding one that go together?

Like this picture, what do you call the hollow one and the protruding one

  • groove or slot, slot tends to be more usual for self-assembly instructions, as both a noun and a verb "to slot something in a slot".
    – Lee Leon
    Commented Feb 14, 2018 at 11:19
  • 2
    The protruding part can be called a TAB. It's almost a stock running gag with "some assembly required" toys: Insert TAB A into SLOT B. See illustration. For assistance, dial 1-800-....-....
    – cobaltduck
    Commented Feb 14, 2018 at 12:28
  • @cobaltduck The main problem with that is that the word slot already applies to the guidance and power slots that power and guide the cars. I like tab but I think that the tabs fit into sockets in this case.
    – BoldBen
    Commented Feb 14, 2018 at 16:18
  • male and female fittings or connectors
    – lbf
    Commented Mar 16, 2018 at 13:19
  • Didn't the game come with instructions (with labels pointing at the different protrusions and indentations)?
    – Mitch
    Commented Mar 16, 2018 at 16:06

2 Answers 2


All these things you label are either inwards or outwards, indentations or protrusions but of different shape or length.

  • rut - this is usually associated with a road where wheels have made an uneven indentation in the surface. Metaphorically, its also for a 'bad pattern': "My life is in a rut, I have to get out of the habit of comma splicing'
  • dent - yes, this more of an indentation that is damage. It's usually very short and is usually not just a line but crater-like
  • groove - a long thin indentation. The long lines in the surface of the road that the toy cars race along are grooves. And yes, it is also the word for the extremely thin line that a needle follows on a vinyl music record. It's also the source of groovy, I don't know how.
  • hollow - this is a roundish, deeper indentation that is usually not linear
  • ridge - this is the upper edge of something sticking out, like a mountain ridge.
  • channel - this is a deeper and wider groove, its width much narrower than its length
  • slot - the one you left out. This is the label for the game. The groove for the cars is also called a slot.

All this, and really you are asking about the connecting parts. Those are usually labeled 'tab' (the thing sticking out) and 'slot' (the narrow hole that the tab fits into snugly).


These might be grooves or recesses, depending on topography and extent etc. If you add an image or sketch, that would help clarify.

  • Thanks for the photo @Toshiyuki San. Yes, those 2 look to me like cylindrical (perhaps annular) connection recesses.
    – MikeRoger
    Commented Feb 14, 2018 at 12:08

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