Abstract: A former for use in a core sandwich of composite reinforced plastics material, the former comprising a rib section (5) divided into a plurality of sub-sections (8) by slits or openings (10) extending partway through said rib section (5) to define a hinge or web section (11) between each adjacent sub-section. A sheet former (22) may be produced by a number of parallel rib sections (5) each joined to adjacent rib sections by a flexible bridge portion (20) to define openings (25) in the former between each bridge portion (20) and the rib sections (5) and/or sub-sections (8). Venting between the sub-sections (8) may be provided by a venting channel (21) formed in the bridge portion (20). An array of upstanding formations (30) each joined at their base 31 by a flexible bridge portion (20) to produce a former sheet (22) is also disclosed. The bridge portion (20) allows venting between these formations through a channel (21) and allows bonding through openings (25) in the sheet (22).