How to check for open polylines in file?

[peckerwood344]

Is there are command to check a drawing for open polylines before I send a file off? What does it look like if the line is open? Trying to create files for cnc. The person I sent the file to said one of my lines was open. I honestly suspect it's his CAM software. He's running Millwright 6. (I know nothing about it.) 

Also, he had trouble opening the file I made in acad for mac 2015. He had me save it in acad 2000. If I save the file in an older version could this be when lines open up? I went in and checked the line and it still looks like the spline I drew with 23 points.

If I select all and then click "join" will this change the shape of the lines? 

I'm attaching the files. He said in Sheet 2 the spline was open in the shape that's the 4th from the left. In Sheet 1 he couldn't close the spline. It's the second to the last shape.

Thanks for your help.