Need 3 bolts
1/4 X 1-1/2 long with 3 matching nuts
3 springs about 1" (25mm) long that would fit thru those bolts.
When calibrating, those nuts get tighten very lightly. Freely spin them until they encounter ANY resistance.
For that reason, nuts must spin freely on those bolts all the way thru.
1 screw for wood (construction screw) Longer then 1/2 (10mm) but no longer then 1" (25mm)
1 3/8 X 1/2 long bolt with matching nut
Those are for the top.