Building Double Crossovers With a Fast Tracks Assembly Fixture May 10, 2019 19:23 These instructions apply to all scales and sizes of Crossovers. Click here or on the image to download your copy now. Related articles Building Crossings With A Fast Tracks Assembly Fixture Building A Double Slip Switch With A Fast Tracks Assembly Fixture Building Turnouts Using Fast Tracks Assembly Fixtures. Building Curved (and Straight) Turnouts With Fast Tracks TwistTies Building A Stub Switch Using A Fast Tracks Assembly Fixture.