If the hole for them goes the whole way through the playfield, you can use a small screw from underneath to hold in place.

If no hole the whole way through. I'd carefully remove the wireform. Put some 5 minute epoxy in the hole. Stick the wireform back in.

LTG : )

I like the screw from the bottom idea! Almost worth drilling it through to do that! Epoxy is a no no to me- its a guaranteed fix an operator would love but later on you risk destroying a bunch of playfield if you have to pull them up (restore etc) and the epoxy holds the top bit of ply better than the bottom bit- you will delaminate a small section and be stuck with a repair you dont want to make (not gonna be a big deal but possible).

Just my 2c

If hole does not go all the way through then break off a small part of wood skewer and put it in the hole to prevent wire frm dropping.

I've rectified this before by setting it where I want it (where the metal is flush with underside of the playfield) and then putting a small dab of kwikwood over each hole on the underside of the playfield. Kwikwood will dry as hard as the real wood and cover the hole up so it won't slide down further. One I did it on over a year and half ago has been on location with over 10,000 plays and hasn't sunk at all since.