A well-maintained slide should move under its own weight with the trombone held horizontally and given a gentle push, gliding rather than requiring force. Test the slide in all seven positions, checking for consistent resistance rather than tight spots at certain positions, which usually indicate a slight bend in the inner slide even without a visible dent. Check the outer slide's hand grip and brace for looseness, since a wobbly brace changes how the slide tracks even if the tubes themselves are fine. Modern synthetic slide lubricants (cream plus water spray systems) work noticeably better than old-style oil alone, so a slide that seems merely "okay" might improve significantly with proper current-generation lubrication before assuming mechanical wear.