Hook for metal garage shelves

I've been using these inexpensive garage shelves for organising components and kit in my workshop. They're great for what they cost and hold a lot of weight. They come in various widths, depths and height, but they're all based on this kind of design...

[180cm x 90cm x 45cm, Black 5 Tier (175KG Per Shelf) Garage Storage Shelving Units](https://www.amazon.co.uk/Capacity-Garage-Storage-Shelving-Warranty/dp/B01HL3VH32/ref=as_li_ss_tl?keywords=Black+5+tier+shelving+units&qid=1565349626&s=diy&sr=1