Correction Fluid

Please note that the content of this book primarily consists of articles
available from Wikipedia or other free sources online. A correction
fluid is an opaque, white fluid applied to paper to mask errors in text.
Once dried, it can be written over. It is typically packaged in small
bottles, and the lid has an attached brush (or a triangular piece of
foam) which dips into the bottle. The brush is used to apply the fluid
onto the paper.