What is a Box?

[RONNCC]

Sorry, I was reading the How to Save Weight guide (http://www.chiefdelphi.com/media/papers/2220) and came across:


Replace 1/8th 1x1 inch Aluminum box with 1/16th wall 1x1 inch aluminum box. 50% weight reduction. Also good for ¼ pound/foot.
If using box as a tension strut try using angle or some stringer from aircraft spruce (at 11 oz. per 12 foot, it doesn’t get much lighter).


1) what is a box?
2) what is a tension strut?

thanks.