~ This kind of puzzle is a step above your simple tangled nails ~
The side bars at the ends of each s-curve adds another degree of difficulty in trying to solve it . However, as with almost all puzzles, once the trick is learned, the solution is very easy .
I have described the 'trick' with great detail . As always, there is absolutely NO force required to get through the solution -- as you will see .
Swing right-hand piece towards s-curve end of left piece
Viewing from underneath, the 'trick' here is to push the bottom bar of the left-hand piece into the loop, while pushing the top bar of the right-hand piece up through the same loop -- in the same move
To allow the action of both bars to easily fit through the loop, you'll notice that the other end of the right-hand piece has been turned upwards a tad -- to allow the action of both bars to fit through the widest part of both loops
Viewing from the top, the remaining pictures show the pieces starting to separate