Repeat previous bar

A one-bar repeat sign replaces the contents of a bar with an instruction to perform the immediately preceding bar again. It repeats the music, not merely the rhythm, unless the score supplies a more specific convention.

Family: Barlines and repeats
Where it sits: On the staff itself
What it looks like: A slash, A dot

Do not confuse it with

The one-bar sign is a single slash with dots; the two-bar sign uses two slashes and spans or centres across two bars.

Tremolo, two strokes

What the sources say

Other Aspects of Notation Open Music Theory
A one-measure or two-measure repeat sign indicates that one should repeat either the previous measure or the previous two measures.
Dorico — Adding bar repeats Steinberg
use bar repeats as a short-hand to tell players to repeat what they did in the previous bar.
SMuFL — Bar repeats W3C Music Notation Community Group
repeat1Bar — Repeat last bar

All notation signs