Have you ever wanted to tie your backpack to the handle of your trolley case but could not fit the backpack's top holder over the handle?
This thing lets you attach the backpacks grip to the handle of your suitcase. You can attach the backpack firmly when you also use the loose ends of the backpack's straps to tie the backpack to the trolley handle.
The grip of my old backpack fit over the trolley handle, but the new one's does not, so I needed a solution to attach my backpack there.
Configure the size to your needs by changing the size values in the FreeCAD spreadsheet. 1 mm smaller in_length than the measured width of the handle makes the part snap nicely to the handle using ABS. YMMV