These screws are very strong and make it very simple to use with the guides you provide. The pieces we produce are 120- 140 year old barn wood pieces! Imagine Black Locust, Black Oak,Red Oak, White Oak, Heart Pine, Hemlock, Chestnut, just to name a few. Your screws hold the wood so tight that it makes the piece look good, nice tight joints with great gripping strength! Never had one fail me and I have purchased the sko3 for 3 years, on several different occasions! They're the best, wouldn't use any thing else!! We love KREGG and are looking to get the DDS #2 square driver kit.