Add easier access to the urukuls switches

Signed-off-by: Egor Savkin <es@m-labs.hk>

src/hw/suservo.md

@@ -16,9 +16,21 @@ With enabled SUServo mode, you only need to add `suservo` to JSON file, with its
 
 ## Setup
 
-On bottoms of each Urukul, switch first pins 1 and 2 to `ON`, as on the picture:
+To enable, on bottoms of each Urukul, switch first switches 1 and 2 to `ON`, as on the picture:
 ![](../img/urukul_pins_suservo.jpeg)
 
+### Easier access to the switches (for big racks)
+
+When the crate is assembled, it may be difficult to pull out the cards to access the switches.
+Hence for big racks it may be easier to remove the upper perforated panel. For this:
+1. Unscrew from both sides:
+   ![rack_urukul_switch_access.jpg](../img/rack_urukul_switch_access.jpg)
+2. Remove empty front panels
+3. Gently push out the perforated panel, applying the force from rack's back and front
+4. With tweezers and following the [basic operating hints](../build_test_firmware.md#operating-hints-and-warnings) 
+   switch the switches in desired direction
+5. Install the perforated and front panels back, screw the screws
+
 ## Testing
 
 After running `artiq_sinara_test`: