Bleaching knots lightens the tiny dark dots where hair is tied into lace. Done well, the lace looks more like scalp. Done badly, the hairline sheds, turns orange, or weakens.
Use a thick mixture
The bleach should be paste-like, not runny. If it seeps through the lace, it can bleach the roots of the hair instead of just the knots.
Go slower as a beginner
Lower developer and frequent checking are safer than strong developer and confidence. Check every few minutes. Rinse when the knots soften in color, not when they disappear completely.
Neutralize and wash
Rinse thoroughly and use appropriate shampoo to stop processing. Let the lace dry before judging the final result.
Bottom line
Bleach knots only when the wig needs it. If the lace is already delicate or the knots are light, makeup on the part may be safer.