There’s a total of 8 jumpers on the board. A standard triwave should have all of them filled. Typically as you add certain mods (wave/sym/drum-trig/bypass), you remove a jumper and insert the mod at that point.
Three jumpers marked “-link-”. Two are above the 555 chips, these are always required. The third is on the side of a 4558 chip: this is required unless you’re doing Drum Trigger Mod or Bypass switch (see the drum trig diagram)
Two jumpers marked “-l-” right next to each other. These are required unless you’re doing Drum Trigger Mod (see the drum trig diagram).
Three jumpers marked “WAVE” in tiny letters. Each one is below a 4558 chip. These are required unless you’re doing Wave and/or Symmetry mod (see the wave/sym diagram)