Repeat previous two bars

A two-bar repeat sign replaces two bars with an instruction to perform the immediately preceding two-bar unit again. Read it as one two-bar pattern, not as two separate one-bar repeats.

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 two-bar sign uses two slashes and applies across two bars; the one-bar sign uses one slash in one bar.

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.
SMuFL — Bar repeats W3C Music Notation Community Group
repeat2Bars — Repeat last two bars
Dorico Pro — Repeat Structures Steinberg
different types of repeat structures, including repeat endings and segments, repeat markers, single-note and multi-note tremolos, bar repeats

All notation signs