i would imagine that after a few reps you will end up sliding accross the floor away from the apparatus, something fixed to floor to hold on to may be a good idea
I wouldn't bother with such a device personally. The chains them selves being attached to the wall will obviously limit the amount of weight that can be safely used, not to mention safely escaped from if you fail on your last rep, which is why modern presses have the sliding lockable bars.
To be honest if your able to lift such a board with your hands then your probably not going to benefit much from it as a leg press. There is also the problem of the position that you will be laying in which appears to give rather crude support to your back and I imagine you would probably spend more time sliding up the floor away from it.
Overall it looks like a terrible design from the days when weight lifting was not well understood and I personally would go the extra mile and make a better, stronger and safer device.
A decent leg press with 100kg+ on that device would be dangerous I think.