Our 1930's home has front and back stairs. The front stairs are very sturdy oak, the rears are somewhat flimsy pine. The rears have shown a bit of separation such that the treads and risers have a bit of a space, and Im worried that Ill go through at some point. We have been working on the space under the stairs, so I have access, now is the perfect time to shure them up. Looking at the stairs from underneath, they look like this: As you can see, there is a gap at each spot where the tread (?) meets the riser (?) (hope my terms are right). In other words, it's at the point where if I was on the stairs, Im at the furthest forward part of the flat section, right where it hits the vertical section going up. So it's just held in with some nails. I need to close the gap and strengthen it. Should I just nail the old nails back in as a start? Since the wood is old and dry, do I need to take any cautions? If I want to strengthen, how should I best do it? Metal straps like the simpson strong tie things? Should I put (glue?) another block of wood there first to help put more "meat" to nail into? If Im nailing new nails into this wood, which is maybe 1/2" thick, should I predrill first or something to prevent cracking? What size nails should I use? Thanks!