A shoring system for concrete slabs is disclosed. One such system includes a drop head with a beam support member which can be moved between lower and upper positions, and a wedge member which locks the beam support member in its upper position by a translational, sliding movement thereof. Wedge member includes a narrower toe portion and a wider heel portion, and the toe portion is insertable past corresponding engagement surfaces on the post of the drop head, to support the wedge member in its upper position. The beam support member has a lower surface engaged by the wedge member and such lower surface is longitudinally spaced from the upper surface of the beam support member, so that there is open space between the wedge member and the bottom surfaces of beam supported by the upper surface of the beam support member.