Can someone please explain why the top left image is correct and the bottom left image is not? Both of these images have the bolts on the lower half of the wood beam (tension) side.
From what I see in the picture I am getting the impression, that these two are for completely different uses.
The one above seems to refer to connection of two wooden beams on top of a column, such as the following
In that case the entire side for each beam will be moving away from the the center line, however the points near the bottom will be moving the least, therefore less tensile stresses will appear.
The second case (lower left) seems to be a bracket which is used to support a hanging weight, somewhere along the length of the beam. If that is indeed the case, I am guessing the reason why they have that as an incorrect, is that the bottom part of the beam will most likely be in tension, and as such positioning a weight there is like putting a wedge. In that case the top half of the beam will be a better position to put the weight is at the bottom of the beam (see below).