The 1/72nd scale Revell U-Boats have a lot of small railing parts.
They really make a big difference in the detail and quality of the kit. They look complicated, but they fit very easily. The molds are very well done, there was no flash, and the parts had few connections to the sprue so they were easy to remove. They also aligned perfectly with the hull parts, which was very nice.
I used photos from this Osprey book to determine the different armaments to use on the one submarine with the quad 20 mm AA guns.