Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Need to know

These are a stable platform but the receiving or female end needs to be shimed in the connection beneath the track with thin cardboard or a regular wood riser placed next to stacking riser or the track will not be level. This is not a problem for me because I am mounting them as permanent but could be as a building toy. This can also happen with the Thomas track that has the plastic connectors on wooden track.