Mend when the line is changing the fly’s movement. The familiar case is a dry in slow water across a faster tongue: the middle of the line races downstream, tightens and pulls the fly sideways. The same problem can lift a nymph or hurry a streamer out of a useful pocket.

There is no prize for mending every cast. If the line and fly are travelling together, leave them alone. First see whether a shorter cast or a different position would avoid the conflicting current altogether.

A floating line is easiest to lift and reposition. Keep it clean enough to sit high. Use a leader that lets the fly travel naturally without leaving so much slack that you cannot see or respond to a take.

A sinking line calls for more planning. Once submerged, it cannot be lifted and flipped neatly like a floating line. Set the angle and line shape during the cast, before it sinks, and keep the presentation short enough to manage.

Read the bend the current is about to put in the line. Your correction gives it room to bend that way before it starts moving the fly.

In the plate, current runs from left to right. The near water is faster than the far lane holding the fly. The uncorrected line bows downstream; placing a curve upstream gives that fast water some line to work through first. If the line is instead lagging in slower water while the fly runs ahead, a downstream correction may be the useful one. Upstream is not a universal rule.

For an on-water mend, lift enough line to free it from the surface, move the belly and lay it down gently. Start as the cast lands, while there is still slack between the correction and the fly. Watch the fly throughout: if it jumps, you moved too much line or waited too long.

For a reach cast, make the forward cast, then reach the rod to the chosen side as the loop unrolls. Allow line to slip as needed so the reach changes the layout without pulling the fly back. Practise this on a short, easy lane before asking it to solve a difficult one. FlyLife’s mending article explains the difference between corrections made in the air and on the water.

Feed or retrieve loose line as the drift develops. A mend buys time; it does not make an awkward drift last indefinitely.

A big flip after the line is tight. The fly skates. Recast and make a smaller correction earlier.

Mending by habit. An upstream flip can worsen a drift when your line is already behind the fly. Compare their speeds first.

Too much slack after the correction. Recover the spare line without moving the fly. You still need enough contact to recognise a take.

Trying to rescue a submerged belly. Shorten the next cast or shape it in the air. Hauling a sinking line sideways usually moves everything attached to it.

Do the line work from a position you have already assessed. NSW DPIRD’s safety guidance puts checking conditions before fishing and advises against taking risks for tackle or fish. If reaching farther would mean an uncertain step, finish the drift and reset. Check jurisdiction rules for the water you choose.