Cheap trap? Just bring 4 small dino gates, place one where you want to put the trap then place one diagonally so you can put one on the right/left with more accuracy, same thing on the left/right place a large bear trap at the center, shoot the spino, lure it into the trap and place the 4th door behind him. If you want ti be safer place two large bear traps. That's how i did it.

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