These are simply jam jars filled with toys, sweets, blowers, balloons, etc. and are generally sold for £1 each. The stall is very popular and they usually sell out quite quickly. Sometimes there's even a jar or two for the adults. I might even make up a few sewing jars myself for the grown ups.
As the school fete is just 2 days away, I've been organised this year and have been buying the odd thing on shopping trips and have gradually built up various bits and pieces to fill them. To be honest, by the time you've finished you can easily spend £1 per jar, even shopping at the 99p store for multipacks of small toys, but it is all in a good cause and only once a year (well, twice if you count the summer fair too). It is also a useful idea for children's party bags if you have a Christmas party or even for birthday parties and the jars don't cost anything as they've been saved from the recycling for the purpose.
I'm donating a few jars again this year and here's one I finished earlier topped off with covers and labels.
I don't really expect them not to be opened until 25th December. Maybe 25 seconds is more realistic.