A Swing Bridge instead of a Duck Under

[ngauger]

Now... With all this in mind. You determine the length of that horizontal support this way:

First - take a 2 X 4 & cut off a 4" piece. This becomes that Alignment Block above.

The horizontal support is the length of the "open area" (minus) 6" (clearance for the 2-1/2" block and that throw bolt plus clearance for the "vertical" 2 X 4 on the hinge side).

Attach that Alignment block now... As shown above - it should be 3/4" below the level of the layout. (Thickness of the 1 X 6)

So if your open area is 36"...... The length should be 36 - 6= 30" for the length of the Horizontal 2 X 4.

Now - you have the vertical & horizontal finished.. Screw them together as shown in the detail shot below (red Arrow points to the attached area). Make sure they are at right angles. - Use a square if you have to.

   
For the 45 deg support board (2 X 4), I measured from the top of the hinge board 15" and then horizontally - the same 15" (see below).

I made marks & then holding a 2 X 4 against these marks - I marked the new 2 X 4 along the inside edges so I could cut the support board & it would be a 45 degree cut.