To discorages birds from roosting, especially pigeons.
yes some have spikes and some don't.some have bumps and others dont
Most of the time if an animal has spikes, they are there to protect them from predictors.
Track spikes do not have a lot of support for your feet. Some have better support than others. For example, sprinter spikes do not have a heel or an arch. Distance spikes have some cushion for the heel. Overall, it is bad to run in spikes but you can still do it. Some work better than others though. It would be a better idea to run in distance spikes than sprinter spikes.
Lightning rods, metal spikes placed on roofs attached to a grounding wire.
Spikes on caterpillars are not a sign of cocooning.Rather, they occur only on some caterpillar species.
Geoffrey Spikes has written: 'Reactivity studies of some ti-based metallocenes'
The Echinoderm's body is covered in spikes/spines.Some spines/spikes are long, and some are short.
Its a thing of preference because not everyone has the same kinds of spikes. I use the outer 6 on my spikes and put a blunt in for the center but some people only have four places to put spikes. See what you like and just go with that
bird spikes
SOME desert plant have spikes, which reduce the surface area of the leaves so that the loss of water is reduced.
Canadian buildings
I did some looking and I did not find any relatives of Stegosaurus with plates but no tail spikes. The tail spikes, or thagomizers, were used as weapons for self defense against predators.