This tool is excellent for removing over-tightened filters or those that are hard to access. This tool is only for removal, it can NOT be used to install a filter. Only use it on disposable spin-on filters, not on cartridge style filters that use a metal or plastic re-usable housings as the sharp teeth will cause damage.
Here's how to use it in hard to reach locations where you still have access to the end of the filter: Install the wrench on the end of an extension that's long enough to reach the filter. Set the ratchet to the tighten, or right hand direction. Push the wrench against the back of the filter while rotating it the in right hand direction. This will cause the jaws to open and the wrench will slip down over the filter. Now reverse the ratchet and turn it to the left to remove the filter.