I have been putting a new shed up and Making bits for it which may be useful. I added a shelf so thought it may be nice to have some hooks which I could add to the underside which can support tools hanging from them so this is what I came up with.

A base plate as I am calling it with 4 fixing holes to screw to the wooden shelf. 

A central hole to either run 1 long screw through or as I intend to run a long enough bolt. 

The central column goes over the desired screw or bolt and the circular hook bracket has an opening which will accommodate most garden variety handles I have. There is a nut shape recess which I hope will house the correct sized nut I have laying about - though  have many to chose from! (Hoarder or collector of many things ;-) ).

When its all up and installed I will add further photographs.

Photos currently added are of assembly and testing.

Of note the Bolt used is an M3 40mm bolt. I have chosen to use 3 washers to improve rotation.

Also the base plate hole is too big for the allen key bolt so i had to press a hot poker into the end to create a recess and use the smaller circumference spring washer to allow the allen key bolt head to be fully recessed. 

Updated versions so no drilling or melting is required added as individual files Also