There are a few ways, you could use a box cutter with a super sharp blade for instance. The problem is if you slip either the track or you could be in pain.
This is how i did it.
The chiesl size required may be a little different from track to track, i found a chiesl that was the right size and trimmed another old damaged one, i think any old chiesl will do
Place a peice of 2x6 or 2x4 through the track, secure in vise, bench or by a buddy. A couple of light taps with a hammer and your through, if need be trim up the fibres with a box cutter.
This is how i did it.
The chiesl size required may be a little different from track to track, i found a chiesl that was the right size and trimmed another old damaged one, i think any old chiesl will do
Place a peice of 2x6 or 2x4 through the track, secure in vise, bench or by a buddy. A couple of light taps with a hammer and your through, if need be trim up the fibres with a box cutter.