Even the best tool can fail; always use a continuity tester after crimping to verify the pinout. If you'd like to narrow this down, let me know: Are you wiring an entire house or just repairing one cable ?
Uses technology (wires go all the way through the plug). best buy rj45 crimp tool
Look for tools that handle cutting, stripping, and crimping to save space in your kit. Even the best tool can fail; always use