In synastry, the positions from one natal chart are set inside another person's house frame. This is a directional comparison: a planet belongs to its owner, but the house number belongs to the receiver. A’s Venus in B’s fourth house does not imply B’s Venus is in A’s fourth.
Start with the receiving chart
First calculate both natal charts from recorded civil dates, clock times, historical UTC offsets, and birth coordinates. For the A-in-B table, keep A’s planetary longitude and use B’s Ascendant and houses. Reverse those roles for the B-in-A table. If either birth hour is unknown, that person's houses cannot be drawn reliably; a noon placeholder is not an answer.
House overlays and cross-chart aspects answer different geometric questions. An aspect measures the angular distance between a point in A and a point in B. An overlay assigns a point in one chart to a sector in the other. A pair can have many close aspects yet a sparse pattern in one receiving house, or vice versa. Read both natal charts before giving weight to an overlay.
A transparent example
Imagine Person B has a 12° Cancer Ascendant, or 102° tropical longitude, and Person A’s Venus is at 15° Scorpio, or 225°. Under Whole Sign houses, Cancer is house one, Leo house two, Virgo house three, Libra house four, and Scorpio house five. A’s Venus therefore appears in B’s fifth house. Under Equal House, subtract B’s Ascendant: 225° − 102° = 123°. Four complete 30° sectors have been crossed, so this position is also in house five.
Move the imagined Venus to 5° Scorpio, or 215°. Whole Sign still puts it in B’s fifth house. Equal House gives 215° − 102° = 113°: only three complete 30° sectors, so it is in house four. The difference comes from the house boundary, not a changed planet position. This demonstrates why a house label without its method is incomplete. It makes no claim about an actual relationship.
Read a pattern, not a verdict
Traditional readers may ask what themes of a receiving house become more noticeable when the other person's planet is placed there. The fifth house is often used for creative expression and play; the fourth for home and private foundations. Such terms are vocabulary for a conversation, not a diagnosis of attraction, consent, or future conduct. A Venus overlay does not tell you what someone wants. Use actual statements and behavior to answer that.
Check both directions and any close cross-chart aspects, then write down one question rather than a score. For example: “Which shared activities feel playful to each person?” is testable in ordinary life. If a birth time is rounded, use the birth-time window tool to see whether a house label changes across the plausible clock interval. Near a boundary, withholding a house claim is more honest than choosing the preferred result.