I purchased these rails for a new king size Simmons mattress set. Looking at the directions, you may find yourself saying 'what?' It's actually a very simple five step process. Empty box and make sure all the contents is there. Lay out the head and foot rails. Place the extender bars over the head and foot and place them according to the width of your mattress....use a measuring tape if necessary to get accurate hole line up...which I found to be easiest way to go about it....then lock the extender bars in place by simply pulling them tight until you hear the snap. After that, position the middle support bar in the middle section of the frame and bolt with one bolt and nut, at top and bottom of frame. After that, place the glider cups on the middle support bar...this will raise the rest of the frame on one side...now it's easy to place the wheels on one side....the other side will lift, place the wheels on the other side. After that, you can make sure all wheels and glider cups are fully inserted. You could take a hammer and bang down slightly if they are not fulling inserted, that'l do it. Not sure why some thought it was difficult to put together. I put it together by myself and I am a woman. It probably took me about 15 to 20 minutes. Great purchase!