Sheets of a vessel or other construction are joined edge to edge by deforming an edge of each sheet to have a projection outstanding from one face of the sheet, the deformed edge is entered into a slot of a joining strip and the outstanding projections are moved across in the slot so that they engage behind an abutment existing in a wall of the slot, and a key is also inserted in the slot to bear against the other face of the sheet and thereby maintain the engagement of the projections with the abutment. The ends of joining strip are then clamped between clamping blocks with such pressure that sliding movement of the sheet edge within its slot is inhibited and the slot is prevented from opening, e.g. upon impact forces.