A joint system for joining together at least two sheet portions, comprising: a first sheet portion presenting a first recess; a second sheet portion, overlapping the first sheet portion, and presenting a second recess, the first and second recesses (5,5') being substantially aligned; and a fastener received in said first and second recesses (5,5'); wherein the fastener is a mainly radially operating fastener, wherein the mainly radially operating fastener comprises: a guide part having an outer substantially conical surface; an expander sleeve having an inner substantially conical surface, adapted to cooperate with the outer conical surface of the guide part, and an outer surface adapted for engaging a radially adjacent surface of at least one of the first and second recesses (5,5'); and a clamping arrangement, arranged to provide an axial relative movement between the guide part and the expander sleeve, thus causing the expander sleeve to expand radially, wherein the mainly radially operating fastener further includes a second outer conical surface and a second expander sleeve operating in opposite direction to said first expander sleeve, wherein the first expander sleeve is adapted for interaction only with the first recess, and wherein the second expander sleeve is adapted for interaction only with the second recess. characterised in that the joint system further comprises a mainly axially operating fastener, and that said the guide part is integrated with the clamping arrangement, wherein the clamping arrangement comprises a through going pin forming an integrated part with the guide part. a first sheet portion presenting a first recess; a second sheet portion, overlapping the first sheet portion, and presenting a second recess, the first and second recesses (5,5') being substantially aligned; and a fastener received in said first and second recesses (5,5'); wherein the fastener is a mainly radially operating fastener, wherein the mainly radially operating fastener comprises: a guide part having an outer substantially conical surface; an expander sleeve having an inner substantially conical surface, adapted to cooperate with the outer conical surface of the guide part, and an outer surface adapted for engaging a radially adjacent surface of at least one of the first and second recesses (5,5'); and a clamping arrangement, arranged to provide an axial relative movement between the guide part and the expander sleeve, thus causing the expander sleeve to expand radially, a guide part having an outer substantially conical surface; an expander sleeve having an inner substantially conical surface, adapted to cooperate with the outer conical surface of the guide part, and an outer surface adapted for engaging a radially adjacent surface of at least one of the first and second recesses (5,5'); and a clamping arrangement, arranged to provide an axial relative movement between the guide part and the expander sleeve, thus causing the expander sleeve to expand radially, wherein the mainly radially operating fastener further includes a second outer conical surface and a second expander sleeve operating in opposite direction to said first expander sleeve, wherein the first expander sleeve is adapted for interaction only with the first recess, and wherein the second expander sleeve is adapted for interaction only with the second recess. characterised in that the joint system further comprises a mainly axially operating fastener, and that said the guide part is integrated with the clamping arrangement, wherein the clamping arrangement comprises a through going pin forming an integrated part with the guide part.