Joiner by trade, updating benches and machine stands to aluminum extrusion. Help!

Dear all

I am very new to working with extruded aluminium but can see the benefits of doing so. I have drawn up plans and designs for a number of updates to my joinery workshop. I am about to pull the trigger and place my order for all the required parts and components but there is something I simply cannot fathom and really have struggled to locate much online regarding this. Basically, where can I purchase a drilling guide for 4040 Bosch Rexroth extrusion. My projects are based upon joining the profiles using the drill and tap method but how on earth do I drill the access hole perfectly accurately without some form of jig or guide. I have found incredibly expensive ones on the net but was wondering if anyone had a tip or a link to where I can get one from. Unfortunately I don't own a 3d printer but happy to pay someone to print one for me if that's what it takes. I have a drill press but without a guide or jig I just cannot see how to drill mm perfect holes to ensure accuracy. Thank you

Never used extrusion, but thought it was assembled with angle brackets and T bolts ?. if you want to drill a hole through the section you will require a steel sleeve(preferably hardened) of the required size, ie tapping or clearance. rough out a piece of oak or similar hard wood say 100mm long and square section larger than the slots in the profile, drill a hole slightly smaller than the OD of your sleeve in the centre at whatever distance from the end suits your needs and press in the bush, thickness the wood to get the bush dead central and a good fit in your extrusion slot and your hole will be central to the slot.
Regards
Mike