Jon, if you go back to the Ask Bob page, you will see a link to Frequently Asked Questions (FAQ) there. It is not the same FAQ page that is at the top of this board. The FAQ page linked from Ask Bob has a section on floors and near the top is information on Cobblewood floors. This should give you a source for the information that you need on this subject. But I believe that Vern wanted to use a filler between horizontally laid boards and not between end grain blocks. These are totally different situations.