Word choice: rut, dent, groove, hollow, ridge, channel

Solution 1:

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).