The clone stamp tool is similar to the paintbrush tool but instead of painting with a single color, you can paint with other existing pixels in an image. The clone tool can be very useful for blending parts of your image together, copying existing elements in the image, and seamlessly removing parts of your image. You can find many tutorials about using the clone stamp tool online. Watch this video for a short introduction: http://ww2.kqed.org/education/2015/03/26/using-the-clone-stamp-tool-in-pixlr-editor/

The clone stamp tool looks like this in the toolbar:

Start with the sample image of the house:

Use the clone stamp tool to remove the wires from the sky and the telephone pole from the sky and in front of the house.

Start by zooming in on part of the image with sky and wires and select the clone stamp tool.

The default brush size may be too big. Change the brush size using the tool option bar. Once you've selected an appropriate size, you need to set the area you're going to clone. Do this by holding the ctrl key on the keyboard and clicking an area of pixels. While you hold down the ctrl key, the cursor will change:

Since we want to paint over the wires with the color of the sky, ctrl-click over a blue area near the wires and release the ctrl key. Once the clone area is set you can use the mouse to click and paint as usual, but now the area under the brush will paint with the reference pixels. Notice how you see the reference point and the brush while you paint with the clone stamp tool:

Follow this procedure to remove all the wires from the sky. You will need to frequently ctrl-click to set a new reference point as you clone different parts of the sky. Also, the reference pixels will always refer to what was there when you first set it; if you just hold down the mouse button while painting you may get some unexpected results such as this:

In the screen shot above, part of the wire on the left was cloned under the brush. Also notice the swath of pixels that are lighter than the sky around it. Those were painted from areas of the sky too far away. Always be aware of your reference point (which will be shown while you paint) and reset as necessary.

By default when you set a reference point the same area will be cloned whenever you start painting with a new click (if you hold down the mouse button while you paint the reference point will follow the brush). If instead you want a new click to pick up a different part of the image aligned to your brush, select the 'Aligned' option in the tool options bar:

Try the clone stamp tool with this option off and on until you get a feel for the difference.

Once you've finished removing the wires from the sky, try removing the telephone pole from the middle of the image. You will need to be very careful cloning grass and parts of the house over the pole so that it blends well. Work in small pieces (zooming and panning) and take your time. Here's an example of the clone stamp tool applied too hastily:

In this example the brush size was too small, the reference area wasn't set correctly and there was too much painting with out lifting the mouse button and clicking again to repaint.

You will need to play with the tool options and brush size to get the right balance. Here's an example of a good start on erasing the pole using the clone stamp tool:

Notice how you can't see any vertical lines from the original pole and that the areas of the grass blend in with each other. The areas above the grass (e.g. the windows, bushes and roof) will be particular tricky. Take your time.