Reading the body language of trees can be important. Knowing what areas of the tree represent a possible defect, and inspecting those areas regularly can save the tree or some property damage.
Co-dominate stems are stems of similar size originating from the same point on the tree. These stems are more likely to fail as they compete for space. They often are associated with included bark. Bark included in branch unions is a defect that lends the tree to a higher likelihood of failure.
In this picture we can see co-dominate stems with a crack developing between them. By inspecting the tree we now know some management option needs to be taken. In this case due to other storm damage (seen in the background) the whole tree needs to be removed.