Could it be: grit in the camera or film cassette?

Continuous lines in the same position across the roll. Fix: Clean the film path and pressure plate with a blower. Check the cassette's felt light trap for grit, especially with bulk-loaded or reused cassettes.

Could it be: handling during processing or drying?

Irregular scratches, or marks that start partway along a frame. Fix: Avoid squeegees and fingers when drying; hold film by the edges.

What went wrong?

There are long scratches along my film

Straight lines running the length of the film, across several frames.

Check this first

Does the scratch run continuously across frames and the gaps between them?

Likely causes

1.
Grit in the camera or film cassette
Common
How to tell
Continuous lines in the same position across the roll.
Fix
Clean the film path and pressure plate with a blower. Check the cassette's felt light trap for grit, especially with bulk-loaded or reused cassettes.
2.
Handling during processing or drying
Occasional
How to tell
Irregular scratches, or marks that start partway along a frame.
Fix
Avoid squeegees and fingers when drying; hold film by the edges.

Avoiding it next time

Blow out the camera before loading.
Store negatives in archival sleeves.

Go deeper

Camera Problems Troubleshooting →
Film Storage and Preservation →

Likely causes

Grit in the camera or film cassette

Handling during processing or drying

Avoiding it next time

Go deeper

Other negatives problems