Sasagaki (ささがき) is when you shave gobo roots like how you sharpen a pencil with a knife.
1. Shave off the gobo skin with the back of a knife.
2. Make a lengthwise cross-shape incision about 1 ½ inch deep at one end. Cut it from that end as if you were sharpening a pencil while constantly rotating with the other hand. Soak in the water or vinegar water to prevent from changing color.