Use the under dash panel as a guide. The rubber donut goes under the vent first to loosely hold the panel in place. Two (sometimes three) large flat headed 90 degree plastic clips hold the panel to the rectangular slotted metal tabs at the firewall. Three (sometimes four) flat 90 degree plastic clips hold the top of the panel to rectangular slots in the under dash panel and steering column. In later 700/900 models with plastic under panels, the upper thumbscrews are instead plastic screws. The upper plastic screws and studs often have a plastic retaining washer on the back side that gets lost, but these washers are unimportant. Use a slot headed stubby screwdriver for all of them. Don't get carried away, if the slots aren't aligned you can mangle the plastic studs.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now