3 x 3 Balusters Attaching To 4 x 12 Stringer
3/8 inch lag screws about 6 inches long
will be used to attach the 3 x 3 balusters to the 4 x 12 stair stringer.
Make sure you drill a 3/8 inch hole through the balusters to avoid
splitting the 3 x 3 as you screw the lags in.
The 2 x 10 will have to be pre drilled with a counter sinking bit to assemble this hand railing. Use 2 inch lag screws.