Input: one of the bars pivoted on the base.
Length of the grey base bar and yellow end bar: a
Length of blue bar: a
Length of green bars: 0.4a + 0.6a
Length of orange bars: 0.4a
Output: the yellow end bar that moves out and gets horizontal position.
The gravity tends to keep the mechanism at folding position.where the mechanism contains two unnecessary bars (in violet and in orange).