I tried to design this as a jack-of-all-extruders to be compatible with both old PEEK-block-and-bolts-mounted hot-ends and groove-mounted hot-ends, with a way to either completely constrain incoming filament or allow it to be pulled away for access to the bolt hobbing. To give it a long name of attribution, it's Andy's-Compatible-Tom's-Guided-Greg's-Hinged-Accessible-Wade's-Geared-Thermoplast-Extruder inhale.The design was something that I edited from Tom's guided extruder before I found the thing page for Greg's Guidler and before I figured out why SolidWorks wouldn't import STLs for editing before. I'm not sure whether the nut-traps will last long if this is printed in ABS due to their proximity to the groovemount holes, although it may be strong enough in PC. Also I don't think the groove-mount holes taken from Tom's design will fit a J-Head Mk.IV, having just got hold of one to measure, so I'm leaving this idea alone for now and working on a version that takes M4 bolts in the idler.As usual I've provided a STEP file for maximum compatibility with different CAD programs, so edit this any way you need to. v1.1 fixes a hole and replaces a cut that I didn't see a reason for before.If you want to be able to easily move filament out of the way when removing a hobbed bolt for cleaning, or just to examine the bolt's teeth, cut away the thin section of the guide facing the idler, and put a bolt through the slot provided to hold your filament in place instead. Remember every extra bolt makes that extruder a heavier lump to move around, so you might even want to just cut a small gap that your filament can clip in/out of.If you want your extruder to be in the old Wade-style right-handed orientation, mirror the STL file in a plating program, or scale the object to X=-1 at the gcode-generating stage.