About the Top Step: You can determine what height you need by measuring the water depth near where you want to locate the steps, near your dock or seawall. Some people like to have the top step at the level of the dock, others will have the top step approximately 8” to 10” beneath the water. When installed this way, the last step is out of the water onto the dock.

Handrails can be installed (on both types) either on the right or left sides. If installing in a boat slip the depth might be a factor and could interfere with your boat. Although most boats don’t draw more than a couple feet of the water, hitting the bottom steps shouldn’t be a problem. Measure to be sure.
Sea Wall Aluminum Free Standing

3 Step - 38 lbs.
4 Step - 50 lbs.
5 Step - 64 lbs.
6 Step - N/A
Plastic Tread & Aluminum Frame

3 Step - 66 lbs.
4 Step - 71 lbs.
5 Step - 76 lbs.
6 Step - 81 lbs.
  In quiet water there is generally no problem Sea Wall, all-aluminum or plastic steps will sit on the bottom or against the dock. But with modern ski boats throwing 3’ wakes, or in rough water, care should be taken to insure your steps don’t wash away. An inexpensive 35 lb. cinder block placed as shown should keep your steps in place. Some customers use common hardware store items like pipe hanger to secure steps.
The all aluminum (Sea Wall steps) have a frame that rests on the lake bottom. A couple concrete blocks on the bottom frame is often enough to secure them.
  installing sea wall steps 
using blocks to help anchor steps Concrete blocks between the legs and the foot can help secure the plastic tread steps. These steps are heavier and a couple concrete blocks should hold them in place.
  Dock Step installation Dock Step installation 
  In areas with a soft or mucky bottom the legs or frame might sink into the bottom. For these installations it’s a good ideal to support the frame or legs with a flat surface. A piece of plywood cut just larger than the frame and bolted to the bottom of the frame or legs will prevent steps from sinking into the bottom.
  sea wall steps standard mounting hardware bracket for seawall steps

Plastic tread steps come with a bracket for attaching them to a dock or sea wall.
Brackets are 37 1/2" center to center. Even if you have a free standing unit, with back legs. It’s not a bad idea to use the hardware. This bracket will secure your steps to the dock.
  common installation items for sea wall steps 
  Common hardware store plumbing items like pipe hanger or straps can also be used.