of openings 14 therein the periphery of each opening 14 is defined by the free ends of resilient fingers 16 defined by the indicated radially extending cut lines extending completely through the paperboard and by the fold lines at their radially outward bases two trap door panels 20 are located centrally of panel 12 with panels 20 defined by a single transverse cut line 22 running at right angles to longitudinal axis 12 of blank 10 fold lines 26 are parallel to and spaced from cut line 22 with other cut lines 24 at the smaller ends of the finger carrying opening defined by folding down or pushing down trap door flaps 20 as will be seen at fig2 the upper portion of panel 12 carries a fold line 30 also transverse to longitudinal axis 12 with panel 32 defining a first reinforcing panel lying above fold line 30 openings 34 are located in panel 32 on respective opposite sides of longitudinal axis 12 the uppermost portion of panel 32 is provided with a recess 36 with free edges 37 being spaced from each other by recess or cut out 36 the axial extent of panel 32 from fold line 30 to free edge 37 is approximately the same as the vertical extent from fold line 30 to cut line 22 so that upon folding panel 32 against the lower surface of main panel 12 panel 32 will occupy approximately half of its area a fold line 38 is located at the bottom edge of main panel 12 and secures second reinforcing panel 40 integrally to main panel.