That bit I am not getting, the parallel guides both locate on the end of the sheet being cut but there is nothing except friction stopping the guide rail moving, if it was lubed then it could slide and I don't see how the guides would stop this as it would just pivot round the first guide. This would also apply to the guide rail system but here it would pivot round the corner of the square.but it cant move inwards due to the locating tabs at EACH end.