The schematic sheet

The tree is the design's real structure, visible from the start:

• Board — one physical board. A project can hold several. Right-click to rename in place.
• Schematics — the sheets under it. Click one to open it. A four-sheet design is four children here, and they share one net space (see Nets, labels and power).
• Layout — the PCB, with its copper layers already listed. It is shown disabled rather than hidden, because the structure it belongs to is the one you are learning now and it shouldn't change shape under you later.
• Library — the parts this document owns.

That last node is the one worth understanding early. Placing a part copies it — symbol, every footprint variant, simulation model, vendor part numbers and all — into the project's own library inside the file. From that point the document resolves everything from its own copy, which means a file you hand to somebody who has never installed a library opens perfectly, forever. Nothing is ever found by path. More in The one-file part library.

These are two different things and eCAD keeps them apart on purpose.

The visible grid follows the zoom. It steps through 10, 25, 50, 100 and 200 mil, always choosing the finest spacing whose dots stay far enough apart to read. It stops coarsening at 200 mil and then fades out instead, so dragging a big block at sheet zoom leaves you a usable reference rather than a haze. Major dots every half inch give you something to count against.

The snap step never follows the zoom. It is a fixed 10 mil at every magnification, with Alt giving the 100-mil lattice symbols are drawn on — the one to hold when you want a row of parts in a dead-straight column. A snap that tracked the visible grid would make the identical drag land on different coordinates depending on how far you happened to be zoomed in, and in a schematic the coordinate is the connection.

Connection snapping outranks both. Within a generous radius, the cursor magnet-snaps to anything a wire can attach to — a pin, a wire or bus end, a wire's body, a junction, a label, a power symbol. Landing a wire on a pin has never depended on the grid step, and the snap is never gated by the Snap toggle: turning off snap must not quietly stop wires from connecting.

A pill at the bottom-centre of the viewport carries four groups:

• Filter — which kinds of thing can be picked at all: parts, wires, labels, power symbols, text, junctions. Covered in Selecting, dragging and editing.
• Sheet — grid on/off, snap on/off.
• Labels — reference designators and values, independently. What you hide here is hidden on paper too, so what you framed is what prints.
• Net highlight — light up the whole net under the cursor rather than the one segment.

A group with something switched off renders tinted, and its tooltip names what is off. That is the entire answer to the classic "why can't I select anything?" — the filter is allowed to persist between sessions precisely because it cannot hide silently.

All of it is per-user, stored on your machine, not in the document. Two people opening the same board see their own view preferences and the same schematic. Title-block metadata is the opposite case — that is document data and saves with the file (see Printing a schematic).

Dimensional values are inches like everywhere else in JetCad3, and symbols sit on the 100-mil pin lattice. Coordinate readouts honour your preferred units.

Component values are not dimensions and never convert. 10k is ten thousand ohms whether you work in inches or millimetres, and 4u7, 2n2, 100nF and 1meg all parse the way an EE would type them. Case matters the way it does in the industry: M is mega, m is milli.