As stated above, it is a gasket. There are stamped-in ridges around all of the ports that get compressed when the intake is torqued down. This is what creates the seal and why the valley pan can't be reused.

 

Mine was like that. it have been re-use before too, cause i can see the lines/mark on the aluminum intake from the vally/turkey pan gasket, when it was re-used it have sealent around all holes and on both sides when i took it of whit the iron intake installed.

 

Full re-usable now, with new rtv / oil/gasoline sealer. Took a vacum clean after over all holes and in the block