So i trying to separate these two legs made from blocks. I want them to be able to move separately but NOT make them independent pieces. I tried using the rip tool but it told me that was an error. Here is a video of me trying to break them. https://webmshare.com/LPOVe
Try selecting the vertices along the middle part using shift, left click and then rip them using v, make sure to select both the back and front vertices
Delete the faces in the middle then rip them. Hide vertices for one side at a time. then creates inside faces for each leg.