L-bracket
An L-shaped plate that lets a camera be mounted on a tripod head in either horizontal or vertical orientation without tilting the head.
In depth
Flopping a ball head into its drop notch to shoot vertically moves the camera off the tripod's axis, unbalancing the load and shifting the composition. An L-bracket keeps the optical axis centred over the legs in both orientations, so switching orientation preserves both stability and framing — essential for panoramas and architecture.
Examples in practice
Rotating a camera to vertical on an L-bracket keeps the horizon in the same place, so a bracketed sequence still merges.