which engages a projection 30 formed in the profiled edge of panel 10 a like projection 31 of panel 11 fits into a shaped portion of the major spine 22 but would if the major and minor spines 22 and 23 were coupled similarly fit into a recess as can be seen in fig1 the major spine 22 has a flat surface 31 which engages against a flat surface 32 of the edge of the panel 10 similarly minor spine 23 engages against flat surface 33 of the edge of panel 10 the joiner element 12 therefore keys onto the profiled edges of panels 10 and 11 as shown in fig1 thus according to the present invention there is no requirement for face to face contact of the respective edges of panels 10 and 11 in order to obtain a secure a robust joint because there is no requirement for deep grooves to accept projections from the joiner element the profiled edges of the acrylic panels are not prone to damage or failure furthermore the high degree of accuracy required to ensure the interface between the edges of the panels as required in wo 99 08575 is no longer a requirement because the panels 10 and 11 of the present invention do not need to fit face to face as an interface e g such as interface 13 the panels 10 and 11 can with suitable.