Abstract: An apparatus for longitudinally cutting a longitudinally moving web has upper and lower guides flanking the web and extending transversely thereof parallel to each other, respective upper and lower blade holders riding on and displaceable along the guides transversely of the web, respective upper and lower blades on the holders engageable with the web, and respective upper and lower threaded adjustment spindles extending through the holders. Respective upper and lower half nuts are movable on the holders between coupled positions threadedly engaging the respective spindles and coupling the respective holders thereto and uncoupled positions out of engagement with the respective spindles. Respective upper and lower clamping rods extend through the holders and respective upper and lower clamping shoes are displaceable on the holders between clamping positions engaging the respective spindles and locking the respective holders thereon and released positions out of engagement with the respective spindles.