Any fort kit is a good idea because it gives the kids designated materials for building forts, rather than messing up the house and stealing all the chairs and couch cushions.
The Fort Kit shown here is only one example. Many others can be found from this source through the following link: Browse all Fort Kit options here.
This Fort Kit is the Toobeez 114 Piece Super Fort Kit. Very versatile and good customer reviews. Read More About it or Buy it Here.
This particular kit is very versatile with 114 pieces for great interchangeability. This one is highly rated by other customers, but of course many others are available too. Check them all out through any of the provided links on this page.
In the case of this exact fort kit shown, it is sort of on the costly side, which is fine if you can afford it, and worth the money. However, many others are available from the same source. Check them all out and make a wise decision.
This fort kit shown here is from a line of kits by Crazy Forts. They make several types of kits including this one.
This is the glow in the dark version of Crazy Forts kits. A 69 piece kit than is interchangeable and lets your kids experiment and be creative with their fort building. The building balls are glow in the dark.
You need to add your own bed sheets or blankets to the project as these things are not included in the box.
The glowing balls will glow for hours at a time. Click the image for a lot more information about this fort kit and how to buy them.
You will also be able to check out other similar fort kits available from this source.
This is an outdoor fort building concept. This is the sno-brick maker to help you build various types of snow structures like igloos and snow forts.
You could even quickly build a snow wall for a snowball fight. Click the image for more details on this fort building kit or to browse through many other types of fort kits available from this source.