Bolt has very low health and is very weak in damaging.
For lower levels, the bolt is used especially for a looting wave or at badly layed out bases where the townhall is on the outside, where Octos /Ichis will distract the towers. Bolts can be used for gaining 4x loot during takedown (meaning when they are damaging, they take 4x the loot than a pokey would, however it does not apply to the takedown bonus)
For a higher level use, because brains are a lot better as far as health and damage for their housing, they can be used if the attacker is low on goo. Bolts can be used for a base with a NEC and a SDT at once, so you can actually time it out for the monsters to take down part of the base and then take the other buildings on, so when a bolt gets flung in it will go straight for the SDT and weed out the Booby Traps .If you have lvl 6 Bolt+lvl 3 teleportation,you could make great Bolt Bomb,Since it can teleport from 1 Harvester to another one/Here,1 video of the bolts bomb
Bolts are not very good in bunkers; there is a reason they are not up there to buy with Shiny. The only reasons you would ever want to use them are (1) for their speed and using precise timing to distract approaching monsters to a power tower, like freezing a single D.A.V.E. at the right moment while a Tesla Tower hits him, and (2) preventing other bunkered monster from being destroyed by Eye-ra, since Bolt can teleport to the Eye-ra to make it explode prematurely. Otherwise, defending is strongly advised against.
Video of Bolts against different monsters: