greenhouse bolts question

They look right to me MoS, same design as the ones that I used. That is assuming that the sizes are a standard. 

Thank you, that's great - I still have some of the ordinary bolts so I'll check for size before I order 

Mine were called "crop-headed" bolts - can be a bit fiddly to tighten as you have to make sure the head has turned through nearly 90⁰ or of course they just pull out (most turn OK as you tighten the nut but of course there's always at least one which wants to have a laugh at your expense!)

 what i did was to get some m6 x30 bolts then cut the sides of the hexagon off to make them fit into the slots it will give you plenty lenght to bolt your shelf too