Line that expands/hides columns

I have provided a link to an XLS file where at the top there is a seperate section with rows 1 and 2 which has a line that can expand/minimise columns T to AF. Can somone tell me what this actually is so I know what to search for in Excel help. Thanks.

Here is the link:
http://www.uploading.com/files/SW2QM...fused.xls.html

I'm sorry about the upload website, it's pretty tacky (you have to scroll down a bit and enter in the number and then hit "Start download").

Thanks guys.