To create this sound I used a large hollow letter G and slid it along a Formica table top. Grandpa-George has an expansive collection of letter Gs from old signs and other sources hanging on one of their walls.

The G that I used to make this sound had not been mounted yet. The material that the letter was made from made a resonant screech when the thin edges of the back side of it slid along the Formica table top.

Screeching Letter G