There is a "security" bolt on the back of the radio, that bolts to a mount under the dash, but it is designed for smallish OEM radios. Generally, when an aftermarket radio is installed, that bracket needs to be removed.
I don't have the rear bracket in mine, only mounted from the front. The deck doesn't bounce or wiggle.
And you really don't need to make any mounts. Unbolt the OEM, and bolt in the aftermarket. There's a bezel that closes in the gaps around the faceplate.
If you buy your stereo from crutchfield.com, they will include all mounting hardware & wiring adapters that you need, iirc, they even included an extension for the OEM antenna, so that it will reach the back of the stereo. You'll pay a little more at crutchfield, but it's worth it to know that you'll have all the parts you need.