The tabs are meant to be kind of "random" I guess would be one way to describe it.

You bend whatever tabs you need to bend, and you bend them in whatever way it takes to get the thing secured. The whole point is that they're different shapes and sizes so that they fit into different kinds of cars.

You have to use your best judgement, and a little bit of "mechanical know-how" to look at how the mounting frame is shaped and decide what/how to bend.

The idea is that the tabs will grip the sled to the mounting frame.

If you don't -HAVE- a mounting frame, then that's your problem.