Use Flip to generate a mirror image of a clip. You can flip frames in a clip horizontally, vertically or both.
To access the Field Merge menu, use:
Timeline, then use ConnectFX (see Creating ConnectFX).
Timeline, then add Timeline FX from the Effects ribbon (see Adding Timeline FX).
Tools, then select from the menu (See Accessing Tools).
This node accepts a front clip, and outputs a result.