By the way, from checkbox we could see the usb devices and their block numbers, SanDisk usb sticks as sda and sdc, by running:

$ sudo checkbox-cli run -t file --transport-where /tmp/submition-device.tar.xz -f com.canonical.plainbox::tar com.canonical.certification::device



<skipped>


path: /devices/pci0004:00/0004:00:03.0/0004:03:00.0/usb2/2-3                                                                                                                                                                                 
name: bus/usb/002/002                                                                                                                                                                                                                        
bus: usb                                                                                                                                                                                                                                     
driver: usb                           
product: Ultra Fit               
vendor: SanDisk Corp.                                       
product_slug: Ultra_Fit               
vendor_slug: SanDisk_Corp. 

path: /devices/pci0004:00/0004:00:03.0/0004:03:00.0/usb2/2-3/2-3:1.0/host0/target0:0:0/0:0:0:0                                                                                                                                               
name: sda                                                                                                                                                                                                                                    
bus: scsi                                                                                                                                                                                                                                    
driver: sd                                                                                                                                                                                                                                   
product: Ultra Fit                                                                                                                                                                                                                           
vendor: SanDisk                                                                                                                                                                                                                              
product_slug: Ultra_Fit                                                                                                                                                                                                                      
vendor_slug: SanDisk 







path: /devices/pci0004:00/0004:00:03.0/0004:03:00.0/usb2/2-4                                                                                                                                                                                 
name: bus/usb/002/003                 
bus: usb                         
driver: usb                                                 
product: Ultra Fit                    
vendor: SanDisk Corp.                                   
product_slug: Ultra_Fit                                                                         
vendor_slug: SanDisk_Corp.


path: /devices/pci0004:00/0004:00:03.0/0004:03:00.0/usb2/2-4/2-4:1.0/host2/target2:0:0/2:0:0:0
name: sdc                             
bus: scsi                              
driver: sd                                                                                    
product: Ultra Fit                                            
vendor: SanDisk                                             
product_slug: Ultra_Fit               
vendor_slug: SanDisk


<skipped>



===

Download the whole output from C3 https://certification.canonical.com/hardware/202107-29307/submission/225210/