After he retired his BT3000, Rod Kirby sent me his original shop made miter fence holder that was famously in all his posts. Typical Rod Kirby craftsmanship. Not that hard to make.
CCF-KIRBY MITER FENCE HOLDER DETAIL.pdf
The above PDF can be downloaded and has the measurements for the holder parts - its rather simple,
Really takes a top plate, a block and a compound T-slot strip, plus you need a 5/16-18 x 3" bolt and a 5/16-18 female threaded knob the latter two can be bought most hardware stores.
I'm pretty sure you can hew this out of a short piece of 2x4 using your BT3000. Rod loved the laminate Marine plywood, but I'm thinking a prime 2x4 would work great.
Knob is 97 cents at Graingers, I put three on will Call COD and picked up at my local Graingers. I think Ace Hardware has them for $4 or 5.
