Mattress Edge Support Options

Modern mattress edge support options include either a foam box edge (10cm strip of high density foam) or pocket spring with a wire side support like the picture above.  Both options help to protect the mattress from sagging on the edges and allow the sleeper to use all the mattress. 

Downsides

Foam box edge can feel different on the edge compared to the middle of the mattress.  If the mattress is soft, the foam edge can feel firmer and you may feel like you are rolling into the center of the mattress.  If the mattress is firm, the edge may feel softer and you may feel like you are rolling out of the mattress.  Foam box edge can weaken and sag over time if you sit on the edge of your mattress often.

Wire and spring edges on inferior mattress can be weak and sag over time if you sit on the edge.

How can you tell if the mattress is constructed well, stand it on its side, does it stands up on or is it floppy and falls over?

Euro or Box Edge Comfort Top

The design of the comfort zone (top of the mattress) also play a role in how much of the mattress you can use and the feeling when you sleep right to the edge of the mattress.  

Euro top is a beveled corner between the side and top of the mattress, meaning you actually loose area on the top, manufactures do this to save money on materials in the construction.  It can also make you feel like you are rolling out of the mattress when on the edge.

Box design gives you a 90 degree edge, allowing you to sleep right to the edge of the mattress. This is important when you have a smaller mattress or a queen/double with two people in it!