Plastic Squeegee that is used for spreading epoxy very thinly. When coating wood thin coats are the best since thicker ones only add weight and mean more sanding.
These are also useful for spreading epoxy over glass fabric quickly.
If, after use, they are left standing vertically the epoxy coat becomes thin and flexing the squeegee when the epoxy is cured will leave the squeegee clean for reuse. They will last for many jobs but you may prefer to have a second one at hand for when the first becomes very sticky in the middle of a job.