From the Super Mario Wiki
Bolts (also known as plugs or rivets) are objects that Mario must destroy in level 100m of Donkey Kong. There are eight (six in the Game Boy version) orange bolts that are worth 100 points each. Mario must simply walk, run, or jump across a bolt to remove it. After all of the bolts are gone, the platforms supporting Donkey Kong will collapse, allowing Mario to rescue Pauline. Removing a bolt also creates a gap that Fires cannot cross. If a bolt is removed while a Fire is on top of it, the enemy will become stuck over the gap. This allows Mario to safely jump over the enemy repeatedly to gain bonus points.