The Labware screen shows the detailed specifications of all labware and stacks which are available to you to use in protocol design. If you want to use an item which is not listed, you will need to download it from Community.
The padlock symbol shows that the labware's specification has been verified and approved. It is
then locked, to ensure no inadvertent changes. 
If SPT Labtech application scientists have designed a protocol for your lab, which is not available
for download from Community, it is possible that it will include unapproved labware (the symbol is
an open padlock), which is only for use in that specific protocol.