The Manfrotto SYMPLA Universal Mount can be used to attach various SYMPLA and non-SYMPLA accessories to SYMPLA rods or to any other standard-size 15mm rods.
The device features an open hook design, four 3/8” screw-holes, and two 1/4” screw-holes. Into the open hooks you would slide in your rods. And into the screw-holes you can attach pretty much any 3/8” and 1/4” accessory.
On the inside of the open hooks is a spring-loaded flat bar that you would press on with the rods as you slide the rods in. Once the rods are in, you can lock a lever to secure them tight in place. However, even before you lock the lever, the spring loaded bar will press up against the rods, keeping them in place — not securely but firmly enough to keep the device from sliding off of the rods. (The lever is repositionable. The looser you keep it, the weaker the flat bar will be.)
Some 3/8” and 1/4” SYMPLA accessories that can be attached onto the Universal Mount are the Flexible Mattebox, Shoulder Pad, V-Offset, Body and Lens Supports and Adjustable Handles.