LS1013 Miter Saw

[Bryan]

What part keeps the saw from sliding?

[MikeA]

There are several parts that could cause the saw even when tightened. The most likely is part #344411-2 (fig #131) which is the slide stopper. If that part is broken the slides cannot be locked. Here's a link to the part:

http://www.ereplacementparts.com/slide-stopper-p-576.html

I hope this helps!