Removable inner forestay
Actually the lever is called a Highfield lever. They are part of quick release system. It is very inportant to install the lever so that the lever swings down and not up when it opens.
There are several other aspects to consider when installing a jibstay or babystay. These stays can pull up in the deck with a lot of force. The above deck point of attachment should be installed in a portion of the deck that has been reinforced for that purpose and below deck there should either be a bulkead or a tesion rod that ties the attachment point from the deck to the hull.
How big a boat are you thinking of doing this on?