super glue!
Depending on the size and weight of your boxes/subwoofers you can use metal or wood cross members going across the bottom of your hatch/trunk area that are either bolted down or liquid nailed down and then have a lip on your box that can be screwed into or use hole nuts in to bolt down....I wouldnt try liquid nails though if the box is big and or the sub+enclosure weighs over 40 lbs or so. Its pretty hard though to make something practicle and strong though in case of an accident...I have seen many braces out last the wood of the box where the top 4/5's of the box plus woofer still flew forward because the box broke.
Depending on the size and weight of your boxes/subwoofers you can use metal or wood cross members going across the bottom of your hatch/trunk area that are either bolted down or liquid nailed down and then have a lip on your box that can be screwed into or use hole nuts in to bolt down....I wouldnt try liquid nails though if the box is big and or the sub+enclosure weighs over 40 lbs or so. Its pretty hard though to make something practicle and strong though in case of an accident...I have seen many braces out last the wood of the box where the top 4/5's of the box plus woofer still flew forward because the box broke.
