This paper presents a novel approach to watermark FPGA designs on the netlist level. We restrict the dynamically addressable part of the logic table, thus freeing space for insertion of signature bits into lookup tables (LUTs). In this way, we tightly integrate the watermark with the design so that simply removing mark carrying components would damage the intellectual property core. Converting functional LUTs to LUT-based RAMs or shift registers prevents deletion due to optimization. With this technique, we take watermark carrying components out of the scope of optimization algorithms to achieve complete transparency towards development environments. We can extract the marks from the bitfile of an FPGA. The method was tested on a Xilinx Virtex-II Pro FPGA and showed low overhead in terms of timing and resources at a reasonable number of water-marked cells.