Start by asking which way the fence is working. Keeping animals out of a hazard and keeping them out of a facility produce different details, and specifying before that question is answered produces a fence that does neither well. The details that change are all at the bottom: a smaller mesh aperture at the base or a fine-mesh apron where small ground-dwelling species are the concern, and a buried or turned-out skirt where digging under the line is. Height is rarely the answer — most incursions happen underneath a fence, not over it, which is why a taller fence with the same bottom detail changes nothing.
Whether a topping is acceptable at all is the land manager's call. On a boundary adjoining reserve land, what can be built — including whether a barbed or razor top is permitted, and whether the alignment can be cleared at all — is decided by the land manager and the council, not by preference and not by a contractor. Ask before you specify. Where a smooth top is required, the security has to come from mesh aperture, correct tension and gate hardware instead, which is achievable but has to be designed in rather than substituted at the end.
Bushland is hard on the bottom of a fence. Constant leaf litter holds moisture against the base, so corrosion starts low and works up on the side nobody inspects. Hot-dip galvanised is the minimum sensible specification on a bushland run, with PVC coating where litter and moisture sit against the base year-round, and the bottom detail kept clear of the litter line where the setting allows. Falling limbs are the other reality, and chain wire's practical answer to them is repairability: a struck section is cut out and replaced in a day rather than requiring a new run. Overhanging deadwood along the line is worth identifying before the fence goes in.
Access control is a gate problem, not a fence problem. A bushland boundary usually has to stop motorbikes and unauthorised entry while staying open to rangers, fire crews and maintenance vehicles. That is solved with vehicle gates keyed to the relevant authorities, formalised pedestrian entries on established walking routes, and bollards or offset entries where the aim is to let people through on foot and stop a trail bike. Fencing a desire line without giving people somewhere legitimate to go generally produces a hole in the fence within a season.
