Can my employees share tools between themselves without checking them back in?

Yes

Field transfer is available on the paid Enterprise version since it allows employees connected through the company to share tools with each other (that are not directly connected). When available, swiping left on a borrowed tool view will show the transfer option to employees. If a tool is checked out (unavailable or borrowed), any employee can initiate a transfer that has to be accepted by either the transferor or transferee. The tool will be updated in the database with the new party in possession thus relieving the tool administrator of this task. In the free version of the app all tools are personally owned by individuals. Thus, they can only be checked out or checked in. You cannot transfer a tool from person to person as there are not indirect connections between people without the Enterprise web interface.