Many years ago I bought a box of Christmas decorations on a Sunday car boot, I paid £2 if memory serves me right and I didn't check the contents first, trusting to fortune. Upon checking the box at home I found lurking at the bottom of the box a plastic toy Father Christmas with a pair of independant waggly legs and with a toy sack behind him with a single wheel underneath it. It balanced when stood on a flat surface but as soon as the surface was made into a slight incline it came to life and started to trundle in a weird but fascinating way down the incline. It did this on its own with no mechanical power source and without being held. I discovered that these toys are called Ramp Walkers or Gravity Walkers or Slope Walkers and that there are loads of them to be found. In America you can find 'Wilson Walkies' and they are made of cardboard cotton bobbins and many different characters - I've got nine of those so far, they date to the 1930's to the 1950's and were made first in America and then later in Canada. There are 1000's of different Ramp Walkers to be found and I've got around 100 of them. They don't turn up too often on car boots and when they do it is often in a box of toys under a table. I'm always on the lookout for new ones to add.
While searching for Ramp Walkers I came across another series of toys that could walk down slopes unaided, these are called Shufflies and moved using a patent design of metal balls held in slots in a metal frame fitted to the bottom of the toys. The movement of the balls in the slots causes a rocking motion in the toy and causes it to move down grooved walkways in Shufflie hospitals, Police Stations, Farms and Castles. Characters can be found that matched the buildings. I'm still looking for the Knight on his horse and I think the castle had a ghost. When they turn up on car boots they are usually in boxes of toys under the tables and so take some seeking out. The boxed sets are very hard to find, and can be expensive, I'm still looking out for my first one.