Loft ladders generally come in two versions: either aluminum or wooden. However, although personal preference will dictate which one will be right for you and the situation you are in, they are both fitted and attached the exact same way. As a result, you can use these directions to fit any type of loft ladder to nearly any loft.
Set up your ladder so that you can attach the brackets. With every loft ladder will come a pair of brackets to fit. Put your ladder underneath the actual loft and climb up to the level of the attachment point.
Mark the exact point of attachment. The brackets should be attached to actual roof joists of the loft since they will be the most stable, and they will have adjustments for joining the loft ladder to them no matter the width of your joists. Measure the top of your joists from the roof down to precisely where you want your loft ladder to attach. You'll need this exact measurement on the other joist as well. Mark them with your pencil.
Use your drill gun and self-threading screws to attach the first bracket to the joist at the exact measurement point. Do the same to the next bracket on the other joist.
Attach the ladder to the brackets. Unfold your loft ladder and bring it up to the brackets. With the supplied pins, take the end of the loft ladder and attach it to the loft ladder brackets. There will be a wing nut on the brackets to adjust for width, and you can adjust this as the ladder stands next to you for a perfect fit.
Test your ladder several times. Once the pins are in place, fold up the loft ladder and make sure all the hinges work smoothly. If you need to, you can spray them down with a little spray lube so that they will open and close effortlessly.