He looks like a used car salesman, but he's really on the level, so you can trust him.
Origin of on-the-level
See the Citations page for examples showing the sense evolution.
On-the-level Sentence Examples
Finally he kneeled in front of her so that their eyes were on the level.
The soil is not very productive, although agriculture flourishes in the valleys and on the level ground; grain has to be imported to meet the demand.
The city consists of two parts; the modern French town, built on the level ground by the seashore, and the ancient city of the deys, which climbs the steep hill behind the modern town and is crowned by the kasbah or citadel, 400 ft.
I.- being laid on the turnpike road which was crossed Plateat Loughborough on the level.
When, however, a company desires to construct a line on a commercial scale, to acquire land compulsorily, to divert rivers and streams, to cross roads either on the level or by means of bridges, to pass near houses, to build tunnels or viaducts, and to execute all the other works incidental to a.