Clamping down movement of a carriage on a rail

Hi

First post and newbie builder...

I am trying to make a vertical table for a piece of test equipment. The platform that I wish to control will be square in shape and it is critical that it is supported well along at least two edges. I am planning on using two C rails with lead screws at two of the corners. I would connect these with a belt and have it driven by a stepper. I do not wish to add any more complexity with more screws and pulleys, therefore I would like to simply have a V rail with a slider that can lock its position with like a quick release clamp. When I would want to change the position of the platform I would just release the clamps then turn the screws before locking the stage by reclamping my sliders.

What parts could allow the open sldier to do this?

Thanks in advance,