[6pack] what goes in the left footwell above the dimmer foot switch?

[Andrew Packard]

Hi list:

I'm reassembling my TR250. In the driver's footwell, directly above the
dimmer switch, there's a captive speed nut but I forget what screws into it.
Can anyone help?  I thought it was the hazard flasher unit, but there's not
enough clearance for the pedal box with that there.  Thanks in advance for
the help.

Andy