A simple swing, BRIO / Ikea compatible.

One side of the rail contains an inner structure to outweigh the other - so once the train passes the swing, it gets back to position.

Works well with one engine and one wagon, for more there's no space left.

Recommended to print in PLA on 20mm.

Split on two beds (haven't tested the quality if printed on a single bed).

Edit: I have added also the Male to Female version as this was mentioned in the comments multiple times :)