Thanks for all your help. I think I have figured it out. I have not been able to locate any 420's this old but looking at newer ones, I think because these holes are uniform (1.25 inches apart) a rubber molding was designed to fit in all these holes to be used as a non slip grip for the "trapezer's" feet.
By the way. Thanks for the welcome. I will probably have more question. as I have not sailed a
boat this small or this reactive. Thanks again.