The Ballasting Aid is made from laser cut MDF and comes flat packed. All it requires is punching out of the sprue and following the simple instructions to glue it together, using a suitable glue such as Deluxe Materials DLAD-87 Laser Cut Kit Glue. During construction of the OO/HO version, you have a choice to use a guide for 3-rail rather than 2-rail track if necessary.
Once constructed, make sure that the glue is completely dry. Please do this as it avoids errant bits of ballast fixing themselves to the Ballasting Aid (as speaks the bitter voice of experience!), the Ballasting Aid is a nice compact device that sits squarely on the track.
Operation is the same in either gauge - fill the hopper in the top of the Ballasting Aid with your chosen grade/colour of ballast and gently push along the track. The hopper will deposit the ballast on the track and the guides will position and shape it as the Ballasting Aid is moved along. A fairly slow and even action is best but experiment with the speed until you find the one that suits you best.
Once you have completed a section of track it is best to clear and position any stray ballast. I find running a wagon along the track helps clear any errant ballast from the inside of the rails where the flanges of locos/rolling stock run. Also having a stiff brush handy to take away/re-position any unwanted ballast is a good idea too.
When you are happy with the look of you ballast then glue it into position, I personally like using Deluxe Materials Ballast Bond as it is a fast and easy glue to use. If you intend to use the Deluxe Materials Ballast Magic, then you will need to mix this in with the ballast before putting it into the Ballasting Aid.
Overall, a very easy and handy gadget that does exactly as its name describes, aiding ballasting. Perfect for the job of making our model railways look even better.