Multiple computers multiple sketch up versions

I have two computers (one with win7 and other is win10) I had to install sketch up 2015 on win7 and sketch up 2017 on win10. The files are useable on both!any ideas to make them useable on both?

2015 files can be opened with SU2017 without any special gymnastics. If you want to open SketchUp 2017 file on SU2015, you’ll need to back save them to SU2015 by using File>Save as… and setting the correct version.