I did another one with an image of Conrete (from Dosch Designs) on the shadow side of the block, and here I am using the Polygonal Lasso Tool (because all I have are straight lines - for curved, use the Pen Tool the regular Lasso Tool - your choice, or a little of everything to do the job right) to draw blocks around areas I want to mask (or you can hit delete just to get rid of them altogether.