A vertical spring wedge restores a tight fitup against an adjacent structure, such as between an inlet mixer and an adjacent restrainer bracket in a boiling water nuclear reactor jet pump. The vertical spring wedge includes a U-shaped bracket including a pair of guiding portions and a pair of bracket holes. A pair of wedge assemblies are coupled with the bracket, each of the wedge assemblies including a wedge segment attached to a spring-loaded guide rod. The guide rods are displaceable in the bracket holes between a retracted position and an extended position. The wedge segments engage the guiding portions, and a combination of the bracket and wedge assemblies have a first width when the guide rods are in the retracted position and have a second width wider than the first width when the guide rods are in the extended position.