I think I know the answer, but I thought I would ask to make sure. In Satie's Gymnopedies #1, starting at measure 9, there is a chord (BDF(#)) there is a bracket like symbol just under the forte notation that is a straight line with the upper terminus touching the "f" (forte). The line is parallel with the stem of the chord, and has a short 90 degree foot at the bottom. The next four chords have this symbol. At measure 13, the dynamics change to pianissimo and again this symbol exists with the upper terminus of the stem touching the pp. The difference with this symbol is that the 90 short degree appendage is a hat, at the top of the line.
My guess: This is an indication to play the chords forte, but the other notes would be unaffected by the forte designation.
What is this called?