I bought this a few weeks ago from amazon because it has good ratings. However, I'm not sure if I "broke" this part of it or not but, could anyone tell me what this is for? Particularly both the screw in/out thing and the flat thing that slides in and out as you turn it? Basically, the grooves within the sliding part seems to have been worn out and it's not held firmly by the screw's grooves anymore. Hopefully it doesn't make the tool useless!