A prototype negative ion source is in development toward the giant negative ion source for the China Fusion Engineering Test Reactor neutral beam injection system at the Institute of Plasma Physics, Chinese Academy of Sciences. The multiaperture and multichannel grids are the most challengeable during the construction of the prototype negative ion source. The research and development activities for the grid manufacturing method were carried out and divided into detailed design, implementation, and testing phases. Based on a special manufacturing process involving the vacuum brazing technique, some prototype grids were produced. Two prototypes have similar structures to the extraction grid of the prototype negative ion source except for the reduced number of cooling channels. A testing campaign (including dimension inspection, leak tests, thermal imaging tests, and magnetic tests) was carried out. The results demonstrate that the manufacturing process and construction technology can meet the requirements of the extraction grid and can promote the construction of other grids or components having a similar structure.