A single/Simple build can be formed from single cards already in the layout, with or without adding a card from your hand. The player who forms the build becomes its owner. You are only allowed to form a build if you have a card in your hand which can later capture that build.
Examples:
there is a 5, a 3 and a 2 in the layout and you have a 10 in your hand; you can combine the 5, 3 and 2 into a build of 10.there is a 4 and a 5 in the layout and you have a 10 and an ace in your hand; you can play your ace, combining it to the 4 and 5 to make a build of 10. You are not allowed to use cards from any capture pile when creating a single build, after you created your build and there is numbers on the floor and your opponent’s captured pile is equal to your build, only then you can take his pile and make a bigger build.
The video below shows how the player built a 9.
There was an 8 on the floor.