Measure and mark the position of the rail posts so that they are spaced equally apart. Typically, each post is placed between 6 and 8 feet apart when using aluminum pickets for your deck rail system.
Position the first post and mark the mounting hole locations with a pencil. Remove the post and pre-drill the mounting holes with a 5/32-inch drill bit.
Coat each lag bolt, provided with the posts, with non-corrosive exterior silicone caulking prior to fastening the posts. The caulking will seal the mounting holes and prevent rotting of the wood deck and corrosion of the post at the holes.
Place the post back into position and insert the lag bolts into the holes. Use a level to check for plumb then tighten the bolts with an adjustable wrench to secure the post in place.
Position the second post at the marks you made when measuring the spacing. Do not fasten it in place yet.
Measure the distance between the two posts and cut the hand and base rails so that they equal this measurement.
Install the base rail support -- provided with the deck system -- by sliding the bottom channel of the base rail over the top plate of the support. Push the support along the rail to the center position. To ensure that the pickets of your railing stay locked into the rails, one or more base rail supports will be required for each 6- to 8-foot section of railing.
Secure the base rail support to the deck surface with the self-drilling screws provided. If you are using two supports, space them along the rail equal distances apart and secure each to the deck surface. Insert the base rail into the bottom channel of the rail post and fasten this with the self-drilling screws provided.
Insert the handrail into the top channel of the post and fasten this with the self-drilling screws provided. It helps to have an assistant hold the opposite ends of the rails as you do this.
Add a spacer into the bottom channel of the handrail and another spacer into the top channel of the base rail. Insert a picket into the base rail and push the top of the picket into the handrail. Continue inserting first a spacer and then a picket until you reach the second post.
Cut the final spacers so they are flush with the ends of the base rail and the handrail. Insert the base rail into the bottom channel of the second post and check that the post is plumb. Insert silicone-coated lag bolts into the mounting holes then secure the post in place.
Insert the handrail into the top of the second rail and secure both rails with the self-drilling screws provided.