an example can be found on AMOSPro_Examples:Examples/H-6/Help_66.AMOS
Grabs a rectangular screen BLOCK from the screen, and saves it into memory. An optional blitter mask can be created for your block as well. This ensures that colour zero will be treated as transparent when the block is pasted onto the screen.
Get Block n,x,y,width,height
Gets a block with number n from x,y to x+w,y+h on the current screen.
Get Block n,x,y,width,height,mask
If mask=1 then a mask will be generated for your block.