Yes. The true block heater is an electric coil that sticks into the engine through a hole created by removing a frost plug (some larger engines have a block heater on each bank of cylinders).
A frost plug is supposed to fall out of the block if freezing coolant expands because of lousy antifreeze. Rather than cracking the block, the expanding ice forces out the frost plug. In theory. There is, I think, more than one frost plug, so replacing one with a block heater is safe.
The block heater has a long enough wire with an electrical plug on the end that sticks out through the grille, or the hood closes on the wire or whatever. An electrical extension is required at that point, so the block heater can be plugged into a socket.
Less-expensive heaters include the true cheapies that replace the dipstick. Others can be attached to the oil pan.
They are needed on the snow-swept prairies, even if it’s proven that a car can start without one at –40°, because in cold temperatures, motor oil, even full-synthetic 0W-20 or whatever, won’t flow properly, if at all with thicker oil.
Extreme engine wear is the result. As well, the starter motor turns much faster when a car’s been plugged in for four or five hours and there is much less strain on a battery that could be operating at 50-per-cent power or less in the cold. Less wear all around.
My parents had a six-volt '51 Chevy that never failed to start on January mornings if it was plugged in — and sometimes if it wasn’t.
If you’ve never heard a six-volt battery at half-power because of the cold turn over an engine in the winter, you’d wonder how the damn thing could start at all.
There are battery warmers, as well, electric blankets that wrap around the battery and are plugged in. And electric car warmers that heat the interior — the plug wires go through an existing hole in the firewall or a new hole is drilled. Or a car door closes on the wire.
Car warmers keep frost from forming on the windows if the car is parked outside (does nothing for snow) and make a car interior less uncomfortable until the car’s heater kicks in, though as soon as a door is opened, much of the heated air is lost.
There are fewer of those than before, probably because with today’s small cars there is less room for them.