....leave the "hot" in exactly as it is (black screw on THAT 3-way). leave the switch leg out exactly as it is (black screw on THAT 3-way)...
the 4-way switch intercepts the travelers from both 3-way switches.....
both travelers from switch 1 to one side of the 4-way, both travelers from switch...
Those straps wear me out big time. As an electrician for 20 years, I've always hated the construction type knee pads. especially the hard-faced ones.... they'll let your knee slip off a rafter in a heartbeat and spin around too much. they're just a pain. I use the cheap volleyball knee pads from...