From time to time I get asked the question, “can I use the barbell sliders to convert my rack into a Smith machine”? My answer to this is, “as long as your rack has 50mm x 50mm (2″ x 2”) square uprights that are no more than one metre apart (inside measurement) then, yes you can. You will need to drill holes in the uprights and maybe make a pair of safety stops“. Detailed step-by-step instructions on how to build the sliders and safety stops can be found in the HGB build manual.