(a) Heating jig designed for use with the Diatome ultrasonic diamond knife to allow ultrathick sectioning with a commercial ultramicrotome. The ultramicrotome's knife mount is used to clamp the heating jig and knife base in metal-to-metal contact. Three small insulators made from rigid circuit board material help insulate the knife and heating jig. A PID controller (Omega) reads the thermocouple to regulate temperature. (b) BSE image (taken at 6kV) of a sequential pair of 20 μm thick hot knife sections mounted so that their matching faces are facing up. (c) Same sections imaged with SE. Scale bars = 100 μm, (d,e) Zoomed regions of previous imaged in SE at higher magnification. Scale bars = 50 μm, (f,g) Inset regions of previous imaged in SE at higher magnification. Scale bars = 10 μm. Hot knife cut surfaces cut with this improved technique look exceptionally free of damage over a wide area and a wide range of imaging scales.