In eurorack modular systems the modules are mounted to the rails. The length of these rails is typically standardized to HP widths (1 HP = 5.04mm). Note that eurorack rails typically use M3 screws while the industry standard in Germany is M2.5.
Note that in addition to the (two) rails you will need:
- screws that fit the nuts
- square nuts that fit your rails (or something like this)
- screws to screw into the side of your rails
- BGT ("Baugruppenträger") on reichelt. For example this
- Stefan Burbulla of Clicks & Clocks sells already assembled rails/frames. Have a look here. You have to order by mail.
(Note: "Rails" is ambigous. In an elctronic context it can also mean your supply voltages. In our case: ±12V. So if somebody says: connect the opamp to the rails, they don't mean you should connect them to the case, but to ±12V. If some signal hits the rails this means the signal's voltage is higher (or lower) than ±12V and gets clipped).