The Tomahawk Excluder One Way Door Easy Release Door for Opossum & similar sized animals is not for use with squirrels. Per the product page, this is for skunks, cats, rabbits, opossums and similar sized animals, which are all much larger than a squirrel. It likely is too heavy for the squirrel to go through and it could also be an issue of having the actual trap at the other end rather than just being open for them to roam free outside once out of your home. You may want to consider these options, the Tomahawk Model E40 for squirrels, or the Tomahawk Model E50D which is the E40 with a removable trap door on the end in case you still want to catch them and relocate them away from the home.
The Tomahawk Excluder One Way Door E80 and other excluders must be mounted or set horizontally to function properly. If the excluder were to be set in a vertical position with the mounting wings on the top, the door would fall open, allowing the animals to re-enter.
