I've used the DNA Painter WATO tool to determine if certain relationships are possible. I also recently signed up for Ancestry Pro Tools. I had a DNA match to a man at 37 cm, but he did not have a tree attached. In the shared matches I found his sister, with a lower cm number, but with a tree. Some of their other shared matches have a common ancestor. Using the WATO tool has helped me figure out ways we may be related.