A carabiner with an operating lever.

The hole is divided into two by the lever, but there is only one cut. Pass the loop that you don't usually remove through the hole in the back.

When printing, support is required between the lever and the bed and in the hole in the frame. Remove the support and finish with a cutter or file so that the lever can pass through the hole smoothly. Insert the end with the lever while pulling away both ends of the cut as shown in the photo.

ADDED DATA 05.06.2021: To make the finish easier, I also created the data with easy-to-remove support. This may be easier when printing with a 0.4 mm nozzle.