I was bummed out because my good guitar was becoming harder to play. You could see the neck was bending forwards a little bit, and a little bit goes a long way in the resulting effects on playability. It’s nice to have the ‘action’ on the low side if you play the guitar in a less than vigorous manner, and mine was edging in to the Everest region of ‘high’ action. That’s often measured by the space between the top of the 12th fret and the bottom of the low E string, and it’s good to have that come in around 2/16″. There’s other measurements as well, but I started with that one and it came in at 3/16 (maybe a bit more). If I could get the neck to straighten out a little, that should lower the strings. The guitar has a metal rod that’s inside the neck, and you can tighten or loosen it to address this type of situation. My guitar has a 1/4 in. bolt at the top of the truss rod, and I attempted to tweak that but failed. My socket wrench set is metric, and it didn’t get a good purchase on the bolt anyway. So I went to the local home improvement center to get the appropriate tool. I told the Resident Expert that I was looking for a ‘nut driver’, and she responded “that’s gotta hurt”. I explained in more detail what the nut driver was, and realized that I already had this tool somewhere in the garage. Long story short, I came home, tweaked the truss rod a quarter turn, and the guitar plays like a dream.
My success emboldened me to attempt the same thing on the old Yamaha FG 150, which was in the back of the closet. The initial measurement of the 12th fret action came in at about 6/16. A tad high. It was possible to bring it down somewhat with a truss rod adjustment, but then the strings started to come in contact with the frets, so I backed off. Apparently the bridge is pulling up the top of the guitar. I could try sanding down the saddle to compensate for the forward-leaning bridge. May have to look into that.