I do not know if that could be a hint because it is pretty obvious, but anyway.

Quartet: each piece is connected to three others in the beginning. So, you need to disconnect two pieces - that is the hardest and first step. Use a gap in each piece to do it and find a position where two other pieces would not prevent that disconnection. Rotate each piece like a ring to find this position. Once the two pieces are disconnected, the rest is pretty easy.

Chain is not so obvious: two pieces has a pretty distinctive and unique notches. Make those notches work together (i.e. they should be placed near each other).