"Load your Building Block" appears as an option at the bottom of the Building Block features list when constructing an image analysis whilst in the Image Analysis view (as shown in the below screenshot). The feature allows users to load one or more custom building blocks as part of their analysis sequence. Typically Custom Building Blocks are proprietary and are written/generated in collaboration with the Revvity Signals team in order to perform a specific task which can't currently be achieved using the standard built in Building Blocks.