Using the Rectangle Tool (M), create a 10 x 160px shape, add that "black" graphic style and place it as shown in the first image. Duplicate this thin rectangle (Control + C > Control + F), select the copy, drag it to the right and place it as shown in the second image. Select both shapes and hit Control + 8 (or go to Object > Compound Path > Make) to turn them into a simple Compound Path. Select this compound path along with the "main" copy, open the Pathfinder panel (Window > Pathfinder) and click the Intersect button. Make sure that the resulting group is selected and hit Shift + Control + G to Ungroup it.