Hi I was shown how to put glue in to a crack in wood not by a stock maker but by a cabinet restorer and I have used the method ever since. But firstly it is always a good idea to remove any oil or grease from the crack by using a solvent this will help the adhesive to grip properly. The method of getting the adhesive into the crack and the adhesive I prefer to use is fast set epoxy after mixing you place the adhesive along the crack or split then use fine monofilament fishing line to pull the adhesive through the crack starting from the cracks open end.
