Early designs involved a steel tooth design that would fit into pocket welds on the arms. These would snap off over use. The alternative design was to run a bolt through the arms and into the rails. While better it still did not address the issue of bending stretcher rails. Bent hinges also added another issue that would happen from use over time. While not as common as the other problems this issue still led to the failure of many black metal frames.
But if space is at a premium and you will only occasionally sleep on your futon best, than the tri-fold will certainly suffice. The best futon bed mattress is the one that best suits your requirements. Consider the space you have available, and what will be the main function of the futon bed mattress. If the futon is going to be used regularly for sleeping on, then most consumer reviews of futon beds tend to favour the bi-fold futon frame and mattress.
Thinking in these terms will help you to understand the type of futon you may need. Hosting couples will require a full or queen mattress, while having a place for a friend to crash when they need to may only need a single. If you have the room, you may want to purchase a few different futons to allow for flexible options as the need arises. A futon may be listed in different ways, depending on the manufacturer or retailers preference.
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