On My 35-3 they are screws that go into the TAFG.
Historical trivia -- the center line table with folding leaves on our Olson was secured via 5/16" ss lags, a pair in front and a pair in the rear at the bottom part.... down into a piece of teak about two inches by 8 inches, under the sole. Not into the grid, tho.
I thought there was some little bit of flex observed in the screwed down sole when the table was leaned on. I replaced the teak with two pieces of 1/4" aluminum bar stock, drilled and tapped for thru bolts.
Much more significant --I added a short piece of alum. (L) angle between the front of the table center and into the slot on the mast. With that aluminum piece "slotted" into the spar the whole assembly will (and has) withstand a lurching 200# person in a seaway without any flexing.
The original scheme seems to have been adequate, based on experience and hearsay, but the improvement was major, also.
If I had an Ericson of this vintage I might drill and tap for bolts into the TAFG and if there war no frp under one of them, it might warrant a wider pieced of G-10, epoxied to the underside of the sole and tapped.
(Just a random thought and worth less than one cent...)
I have been on some deliveries where the interior furniture - table or shelves - was weak and vulnerable. Humans tend to lurch around without notice in a cross sea.