Wood, especially pine or maple, typically contains sap. When building with wood, it is imperative that the wood has been properly dried to avoid oozing sap. When it has not been properly dried, sap will begin to seep out and cause problems with the finish. The only solution is to scrape the sap off and refinish the wood, and to continue doing this until the wood stops oozing. The process can take several years.
Locate all of the sap marks on your wood.
Scrape off the sap with the 5-way tool. Use the razor blade for especially hard sap that refuses to come off with the 5-way tool.
Sand down the wood until there are no more sap marks left.
Restain the wood and apply a finish if your wood planks have a layer of top coat.
Repeat as necessary until the sap stops seeping out.