BIM Explorer - free
Raise a coordination issue right where you see it. A BCF issue keeps the camera, the selected and hidden elements, the colours, the section plane and a snapshot - so it opens at the same cut in any other BCF tool. Export BCF 2.1 or 3.0 free; import and review other people's issues with BIM Explorer Pro.

Turn on the Section tool in the 3D view and move the cut with the Section height slider.
Select the elements the issue is about, and use display modes or colour by property to make them obvious.
In the BCF tab choose New issue, give it a title and description, type, priority and assignee, then Create issue. The camera, selection, hidden elements, colours, the section and a snapshot are kept with it.
Add comments and change the status. Click the issue to go back to its viewpoint - your own issues bring the section back.
Choose BCF 2.1 or 3.0 and Export .bcfzip. The section is written as a BCF clipping plane, so the issue opens at the same cut in other BCF tools. Importing BCF files is part of BIM Explorer Pro, and imported issues open at their section.
Help: BCF issues and sections has every option in detail.
Free in BIM Explorer. No time limit, no account, no ads, and your models never leave your PC. BIM Explorer Pro is there when you need takeoff, a BOQ, IDS and clash checks.
BCF 2.1 and BCF 3.0, the two in common use. Both exports validate against the buildingSMART schemas.
Yes. The section plane is saved in the viewpoint as a BCF clipping plane. Imported issues from other tools can carry up to six planes (a section box), and BIM Explorer Pro applies them all.
Creating, commenting on and exporting issues is free. Importing BCF files from other tools and reviewing them is part of BIM Explorer Pro.
Yes - a sample BCF file exported by BIM Explorer is on the downloads page.

A 2D plan of any storey, cut at the height you choose, with zoom, pan and a scale bar.

Green has quantities, amber has none - see if a model can be priced before you start.

Lengths, areas and volumes by type or storey, sent to a BOQ that stays linked to the model.

Five ready-made checks - Uniclass, spaces, base quantities, common properties and a handover minimum.

The model tree, every property, display modes, sections and measuring - free and offline.

Colour by IFC class, storey, material or any property, with a legend to hide, isolate and select.

Hard clashes between models or IFC classes, exported as BCF - and what changed between issues.
The IFC viewer is free. BIM Explorer Pro is a one-off £29.99, with a free 7-day trial.