Webs of material guided by rollers tend to move sideways off the correct track. Among other things this leads to print no longer appearing where it should do and to webs not being rewinded accurately.This is where web guiding comes into play. It keeps the material in a defined position and guarantees an exact input feed into the production process even at highest processing speeds.

To summarize: web guiding ensures an accurate running of the web where it would otherwise wobble and shake.