Rear spare doubler

Hello there. Helping do a annual on my fathers RV-12 and on the checklist of items to check is the “REAR SPAR DOUBLER”. Can anyone shed some light on what this is, and where to check. Can’t seem to find it in any AD, service bulletins, or manual. Thank you.
Michael Krause

https://vansairforce.net/community/showthread.php?t=203937

This what you are looking for?

There are instructions on page 3-13 of the maintenance manual. (3-15 for 12iS)

You can also check KAI section 14 for more info.

Instructions for the repair if necessary are near the end of MM section 5.

I think what you are referring to may be the "play" in the rear stub spar. If you grab the wing handle at the wingtip and pull fore and aft, there might be some play. Some is allowed but it shouldn't be much. jrtens already pointed you to the maintenance manual and KAI. Replacement instructions in the MM page 5-23 and you can purchase new W-1207B doublers at the Van's store. They have made available doublers that are slightly oversized as well in case you need them. Pretty inexpensive.

The only other "inspection" item I am aware of for the stub spars is to inspect, clean and re-apply anti-seize paste prior to wing reattach. KAI Section 30 discusses paste and exceptions if the plane is not yet painted.