The early Scalextric cars used a pin to run in the slot of the
Scalextric track rather than a blade used later. Several Scalextric
guides were produced but the most popular was the round pin guide
sometimes known as the Scalextric G3 round pin guide.
There are a few problems with the pin guides:
The pin can snap easily
The pin can wear out
Another problem is where you layout has a crossover for the slots as the pin can change lanes and go onto the other track