Normally you nail model train track to a big board to hold it together. However, If you keep your trains stored away and just bring them out occasionally, as I do, you probably just set a loop up on the floor and only friction holds the tracks together. The heavy the train running around the track tends to pull them apart, especially on the curves. These clips hold two pieces of track together. They go on from the bottom and shouldn't be too hard to install. Just putting 12 or so in the trouble areas of our loop significaly increased the reliability. There were a few spots where the clips didn't fit. Apparently there is some variation between tracks. If you plan to use these, I suggest printing one and trying it first. I've included the SolidWorks file if you need to make adjustments. They each use 1.4g of plastic which makes the cost about 7 cents so you can afford to use a few. I printed 12 at a time with .3mm resolution and they worked well.