[Question] Belt actuator example

Could you please help me understand this? Shown below are two images from the sketchup belt actuator build examples. What I can't understand is how the belt attaches to the plate. Looks like there is an 8mm low profile screw, belt clamp, T-nut, and aluminum spacer; however, I don't think that an aluminum spacer would fit into the channel here. Has anyone built this?
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